Reporting from Washington — The veteran FBI agent and a local sheriff’s deputy took no chances when they got a credible tip about a potential terrorist.
In a joint operation, they ran his name through a maze of federal criminal and terrorism databases and scrutinized his telephone records for suspicious contacts.
Without a warrant, they couldn’t read his emails or listen to his calls. But they watched him from unmarked vehicles to track his daily routine and to see whom he met.
They deployed two confidential informants more than a dozen times to secretly record his conversations. They interviewed him twice and convinced him to provide a written statement — in which he admitted he previously had lied to agents.
In the end, after a counter-terrorism investigation that stretched from May 2013 to March 2014, the agent and his supervisor concluded that Omar Mateen was not a threat and closed the case.
Just over two years later, on June 12, the 29-year-old security guard strode into a packed gay nightclub in Orlando, Fla., and massacred 49 people and wounded dozens more in the worst mass shooting in U.S. history. He pledged allegiance to Islamic State before he was killed by police.
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Inaya Bava, 5, on June 16, 2016, draws on crosses set up to remember the victims of the Pulse nightclub shooting at the Orlando Regional Medical Center.
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Relatives of those killed and wounded in the Pulse nightclub attack arrive at Amway Center on June 16, 2016, for private meetings with President Obama.
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President Barack Obama and Vice President Joe Biden bring flowers to the makeshift memorial at the Dr. Phillips Center for the Performing Arts.
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Jiffy Lube employee Ralph Nieves puts up a sign of support for the Orlando community following the shooting at the Pulse nightclub.
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Sarah Roemer, left, and Brandi Van Dongen, nurses at Arnold Palmer Childrens Hospital in Orlando, pray at one of the memorials.
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The Parliament House is one of the largest nightclubs catering to the LGBT clients.
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Rafael Rivera, left and Jeannette Gonzalez grieve at a wake for Eric Ortiz, one of the victims of the Pulse nightclub shooting.
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Members of the media and public wait to catch a glimpse of President Obama at Amway Center.
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A prayer service is held on June 15, 2016, for the victims of the Pulse Nightclub shooting at Delaney Street Baptist Church in Orlando, Fla.
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Kelly Greenwood prepares a casket on June 16, 2016, at the Cardinal Casket Company in Orlando, Fla.
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Candles are placed under American flags set in a circle outside a vigil at Christ Church Unity for the shooting victims.
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At the Dr. Phillips Center for the Performing Arts, Taylor Green, 25, left, and Brittany Spencer, 25, grieve for those killed in the Pulse nightclub attack.
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ATF investigators continue to work the scene of the Pulse nightclub shooting along Orange Ave.
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Friends and family attend the funeral of Angel Luis Candelario-Padro. It was the first funeral for the 49 victims of the Pulse nightclub shooting.
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Doctors, nurses and first-responders at a prayer service in the emergency room at Florida Hospital in Orlando to honor the victims of the nightclub shooting.
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FBI investigators continue to work at the Pulse nightclub on June 15.
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Mourners embrace outside the visitation for Pulse nightclub shooting victim Javier Jorge-Reyes.
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Mourners gather at the Dr. Phillips Center for the Performing Arts in Orlando for a vigil in honor of the nightclub attack victims.
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Mourners gather at the Dr. Phillips Center for the Performing Arts in Orlando for a vigil in honor of the nightclub attack victims. (Carolyn Cole / Los Angeles Times)
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Mourners gather at the Dr. Phillips Center for the Performing Arts in Orlando for a vigil in honor of the nightclub attack victims. (Carolyn Cole / Los Angeles Times)
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Michelle Moment sing praise during a service at the First Baptist Church of Orlando during a special prayer service for the attack on Pulse nightclub.
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“We were protected, we were saved it was just a miracle,” said Orlando Torres, 52. A promoter at Pulse, Torres was trapped in a bathroom stall with a friend. (Carolyn Cole / Los Angeles Times)
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With stitches in his hand, gunshot victim Angel Colon tells his story to the media at a news conference at Orlando Regional Medical Center on Tuesday.
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Patience Carter after describing the attack on the Pulse nightclub in Orlando. (Carolyn Cole / Los Angeles Times )
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Gunshot victim Patience Carter, 20, left, is consoled by Dr. Neil Finkler at a news conference at Florida Hospital, joined by Dr. Brian Vickaryous, center, and fellow survivor Angel Santiago, 32, right, where they described the attack and its aftermath.
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Angel Santiago on June 14, describes how events unfolded during the mass shooting at the Pulse nightclub in Orlando two days earlier.
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Doctors and other staff at Orlando Regional Medical Center involved in the response to the nightclub shooting answer questions at a news conference on June 14, 2016.
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Thousands gather for a memorial at the Plaza at the Dr. Phillips Performing Arts Center in downtown Orlando on June 13, 2016, to honor those killed and wounded in the Pulse nightclub attack.
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Alison Cossio, center, holds a photo of her friend Christopher Sanfeliz, who one of the victims of the Orlando shooting, during a June 13, 2016, candlelight vigil and rally, hosted by the Los Angeles LGBT Center, at Los Angeles City Hall.
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Rabbi Neil Comess-Daniels plays guitar and sings during the Islamic Center of Southern California and ICUJP Interfaith Vigil Against Violence and Hatred Monday,night in remembrance of the 50 people killed in Orlando.
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Marwa Balkar holds a candle at the Islamic Center of Southern California and ICUJP Interfaith Vigil Against Violence and Hatred on June 13, 2016, in remembrance of the 49 people killed in Orlando, Fla.
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Los Angeles City Hall is lit up in colors of the rainbow during a candlelight vigil and rally, hosted by the Los Angeles LGBT Center.
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Scott Phillips and Em Enagan mourn for the 49 lives lost in the Orlando shooting during a vigil at Los Angeles City Hall.
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A song is sung during a candlelight vigil and rally, hosted by the Los Angeles LGBT Center, at Los Angeles City Hall, for the victims of Sunday’s shooting massacre at a gay nightclub in Orlando.
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Thousands gather for a memorial rally at the Plaza at the Dr. Phillips Performing Arts Center in downtown Orlando on Monday to honor those killed and wounded in the Pulse nightclub attack.
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Madeline Lago, 15, and her mother Carmen Lago were among the thousands who gathered for a memorial at the Plaza at the Dr. Phillips Performing Arts Center in downtown Orlando on Monday to honor those killed and wounded in the Pulse nightclub attack. They bowed their heads as the bell was tolled.
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Thousands gather for a memorial at the Plaza at the Dr. Phillips Performing Arts Center in downtown Orlando on Monday to honor those killed and wounded in the Pulse nightclub attack.
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Friends and relatives bring flowers and remembrances to the plaza at the Dr. Phillips Performing Arts Center in downtown Orlando on Monday.
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Danielle Irigoyen brings flowers to the victims of the Pulse nightclub shooting. “I’m very close to many of the people who go to Pulse. Pulse was a safe place for us all,” she sail.
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Investigators gather at the Pulse nightclub on Monday morning.
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Investigators set up at the Pulse nightclub.
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Family gather for victims at Beardall Senior Center in Orlandoon Monday.
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Friends of Shane Tomlinson, who was killed in the Pulse nightclub shooting, gather in prayer and remembrances in downtown Orlando on Monday. (Carolyn Cole / Los Angeles Times)
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Friends of Shane Tomlinson, including Richie Compton, left, and Erik Winger, right, gather in prayer and remembrances in downtown Orlando on Monday. Shane Tomlinson was killed killed in the Pulse nightclub shooting.
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Family and friends arrive at the Senior Center in Orlando as they await news on their loved ones on Monday. (Carolyn Cole/Los Angeles Times)
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Volunteers gather in prayer on Monday at the Senior Center in Orlando where they are there to help grieving family and friends of those killed and injured in the shooting at Pulse nightclub.
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FBI investigators in Orlando, Fla., look at the floor plans of Pulse nightclub as they gather on Monday morning to continue the investigation.
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People gather at Taylor Square in Sydney, Australia, to show solidarity with victims of the Orlando nightclub shooting.
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City Hall in Tel Aviv, Israel, is lit up in solidarity with Orlando’s shooting victims.
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New Zealand residents gather at Frank Kitts Park in Wellingtond to mourn victims of the Pulse nightclub shooting in Orlando, Fla.
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A man lights a candle in Paris on June 12 to remember those slain and wounded in the Orlando nightclub shooting. (Rapahel Satter / Associated Press)
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New Zealand residents gather in Frank Kitts Park to mourn victims of the Orlando nightclub shooting.
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Residents gather at Joy Metropolitan Community Church near the Pulse nightclub in Orlando to mourn the mass shooting victims of the early morning attack on June 12, 2016.
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Johnpaul Vazquez, right, and his boyfriend Yazan Sale sit by Lake Eola, in downtown Orlando, thinking of those killed and injured.
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Judy Rettig, center, and Dave Hack, left, hug after a prayer service held at the Joy Meropolitan Community Church in Orlando.
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Zafar Basith prays at a vigil for the Orlando shooting victims at the Baitul Hameed Mosque in Chino.
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Raymond Braun, right, right, gets a hug after a vigil held in West Hollywood for the victims of the shooting at the nightclub in Orlando.
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Monte Dobbs and Jhoanna Galvez of Long Beach, comfort each other during a vigil service at the corner of La Cienega Blvd. and Santa Monica Blvd.
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Orlando, second from right, was at the nightclub and trapped for three hours in a bathroom. Orlando and family attend a vigil and church service held at Joy Meropolitan Community Church very close to Pulse nightclub.
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People hug in solaceafter a vigil and church service held at Joy Meropolitan Community Church very close to Pulse nightclub.
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Susan Stephens, right, gets a hug from Karen Castelloes before a vigil and prayer service is held at Joy Meropolitan Community Church very close to Pulse nightclub.
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Investigators view the site of the early morning mass shooting on June 12, 2016, at Pulse nightclub in Orlando.
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People hold signs in support of the Orlando shooting victims on Sunday.
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Kelvin Cobaris, a local clergyman, consoles Orlando city commissioner Patty Sheehan (right) and Terry DeCarlo, an Orlando gay-rights advocate, as they arrive on the scene near where at least 50 people were reportedly shot and killed in Orlando, Fla., Sunday, June 12, 2016.
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Aerial view of the shooting scene at Pulse nightclub in Orlando, Fla.
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A bomb disposal unit checks for explosives around the apartment building where shooting suspect Omar Mateen is believed to have lived on June 12, 2016 in Fort Pierce, Florida.
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Ray Rivera, a DJ at Pulse nightclub, is consoled by a friend outside of the Orlando Police Department after 50 people were killed at the club on Sunday.
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Orlando police officers outside of Pulse nightclub after a fatal shooting and hostage situation on Sunday.
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Terry DeCarlo, executive director of the LGBT Center of Central Florida, right, is comforted by an Orlando Police officer after a shooting involving multiple fatalities at a nightclub in Orlando, Fla. on Sunday.
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An aerial view of the shooting scene at Pulse nightclub in Orlando, Fla. (Red Huber / Orlando Sentinel)
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Los Angeles Mayor Eric Garcetti, center, and others have a moment of silence on June 12, 2016, in West Hollywood for the victims of the shooting in Orlando, Fla., that happened early that morning.
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Emergency personnel at Orlando Regional Medical Center wait with stretchers for the arrival of victims from the fatal nightclub shooting.
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A police officer stands guard outside the Orlando Regional Medical Center after a fatal shooting at nearby Pulse nightclub in Orlando, Fla., on Sunday.
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Law enforcement agencies and local city representatives speak at a news conference after 50 people were killed at the Pulse nightclub in Orlando, Fla.
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An Orange County (Fla.) Sheriff’s Department SWAT member arrives at Pulse nightclub.
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Orlando police direct family members away from the Pulse nightclub, where 50 people were killed.
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Jermaine Towns, left, and Brandon Shuford wait down the street from the Pulse nightclub in Orlando, Fla. (Phelan M. Ebenhack / Associated Press)
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Bystanders wait down the street after a mass shooting at the Pulse nightclub in Orlando, Fla.
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The scene outside Pulse nightclub in Orlando, Fla., after the shooting early Sunday.
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An injured person is escorted out of the Pulse nightclub after a shooting rampage Sunday morning in Orlando, Fla.
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An injured man is escorted out of the Pulse nightclub after a shooting rampage Sunday morning in Orlando, Fla. A gunman with an assault-type rifle and a handgun opened fire inside a gay nightclub, killing at least 50 people before dying in a gunfight with SWAT officers, police said.
(Steven Fernandez / Associated Press) Since then, senior FBI officials have scoured the 3-inch case file from the 2013-2014 investigation to see whether agents had missed clues to his murderous intentions or apparent radicalization.
“We don’t have a crystal ball, unfortunately,” said a senior FBI official, speaking on condition of anonymity because the case remains under investigation. “We went right up to the edge of what we could do legally, and there was just nothing there.”
In interviews with The Times, senior FBI officials provided new details of their early focus on Mateen and some of the lessons they have drawn as the FBI assesses and tracks more than 1,000 suspected extremists across the country.
The 10-month probe remains one of the enduring and frustrating mysteries of Mateen’s deadly rampage at the Pulse nightclub.
The day after the attack, FBI Director James B. Comey broadly outlined the 2013-2014 investigation to reporters. He staunchly defended the bureau, saying he didn’t “see anything in reviewing our work that our agents should have done differently.”
Still, the post-massacre review uncovered a surprising gap.
The senior FBI official said agents could have been more aggressive in accessing Mateen’s social media accounts, including Facebook. But the official noted that in 2013 such checks of online posts were not yet routine or “part of our investigative DNA.”
Today, one of an agent’s first investigative steps is to check a suspect’s social media, especially in light of the Islamic State’s aggressive recruitment efforts on Facebook, Twitter and other digital networks and apps.
In Mateen’s case, it wouldn’t have changed the outcome. The post-shooting review determined his social media accounts contained no ties to terrorist groups.
He did not post radical statements until the night of the shooting, and then just to a group of friends, not the public, according to a second FBI official, who also spoke on condition of anonymity to describe the investigation.
After the shooting, the FBI determined that Mateen’s laptop computer had been used in recent years to view extremist videos online, including grisly beheadings. It also was used to seek information on Islamic State.
Watching offensive videos is not a crime, however, and federal agents did not have the probable cause necessary to obtain a search warrant in 2013 to even learn that much, FBI officials said.
“This was not a baseline shake-the-bushes ... kind of investigation,” said Patrick Skinner, a former CIA case officer and director of special projects for the Soufan Group, a security firm based in New York.
“They looked and didn’t find anything,” he added. “That doesn’t mean that the investigation was bad, or wrong. It shows how difficult it is to get in front of these things.”
The FBI began investigating Mateen in May 2013 after the St. Lucie County Sheriff’s Office reported that the American-born son of Afghan immigrants might pose a threat.
Mateen was a private security guard at the county courthouse, where the Sheriff’s Office oversaw security. Co-workers had warned that Mateen had claimed connections to the terrorist groups Al Qaeda and Hezbollah, and that he wanted to die as a martyr, the Sheriff’s Office told the FBI.
The bureau gets tens of thousands of tips each year from people reporting suspicious activity. Most are discarded after rudimentary investigation.
The FBI took the concerns about Mateen seriously because the report came from another law enforcement agency, because he had access to firearms and because he worked in a public building.
The bureau assigned an FBI agent with at least 10 years of service in the bureau in its Fort Pierce office, and a sheriff’s deputy on the local Joint Terrorism Task Force, to investigate.
The agent was skeptical that Mateen posed a real risk. When Mateen said he was a member of Hezbollah, a Shiite group, and had family ties to Al Qaeda, a Sunni group, it was clear he didn’t know or care they were bitter rivals, the senior FBI official said.
Even so, the agent realized that people becoming radicalized don’t always understand the fine points of jihadist politics, two FBI officials said.
The lead agent opened a preliminary investigation. Under Justice Department guidelines, such an inquiry can run six months and be extended for six more.
The designation permitted the investigators to use a variety of tools — searching databases, obtaining cellphone records and conducting surveillance, for example.
More invasive techniques — such as seeking a warrant from the secretive Foreign Intelligence Surveillance Court to read email and to eavesdrop on phone calls — are reserved for full investigations and then only if the FBI can convince the court there is probable cause of a crime.
While the probe was underway, the FBI added Mateen’s name to the “selectee list” on the bureau’s Terrorist Screening Database, also known as the Terrorist Watchlist.
It would ensure he got special screening at airports and that an FBI agent would be alerted if he tried to buy a gun or was stopped by police. About 1,700 Americans are on the selectee list.
The first search — checking Mateen’s name against criminal and terrorism databases — came up dry. After obtaining his call records from his phone company, the team also ran his number and his contacts through terrorism databases. Again, they found nothing suspicious.
During the next few months, they conducted surveillance of Mateen as he went to work and met friends, but they saw nothing unusual.
They had two confidential informants meet repeatedly with Mateen over the 10 months to see whether he might say something incriminating while they were recording him. The FBI routinely uses informants to gather evidence in terrorism cases, and often relies on them to help set up sting operations.
FBI officials refused to identify the informants or say where they met with Mateen, although a senior FBI official said they had “nothing to with the mosque,” the Islamic Center of Fort Pearce, that Mateen attended.
Mateen admitted to the informants that he had claimed terrorist ties at work. But he said he had been joking, trying to scare co-workers who had bullied him for being a Muslim.
In September 2013, FBI officials said, the lead agent and deputy sheriff interviewed Mateen. He initially denied having made any radical statements.
The investigators returned a month later and accused Mateen of lying. This time, he admitted in a written statement that he had not been truthful, and had in fact claimed terrorist ties because co-workers had teased him for being Muslim.
It was true: When FBI agents interviewed Mateen’s co-workers, they admitted they had teased him about his religion.
“They were being jerks,” said a U.S. counter-terrorism official who also spoke on condition of anonymity. “He wasn’t making that up. He wasn’t paranoid.”
Concerned it might have missed something, the FBI extended the investigation in the fall of 2013. When they closed it in March 2014, they removed Mateen’s name from the Terrorist Watchlist.
The FBI typically only charges someone with lying to agents if there is an underlying crime. In this case, officials said, they had none.
That summer, the FBI came knocking again. The focus this time was Moner Mohammad Abussalha, a former member of Mateen’s mosque who had become a suicide bomber in Syria. Agents scrambled to learn whether he had associates in Florida.
A member of the same mosque told agents that Mateen had mentioned watching online sermons by Anwar Awlaki, the influential American-born Al Qaeda cleric who was killed by a CIA drone in 2011 in Yemen, two FBI officials said.
The man said he didn’t think Mateen was dangerous, but suggested the FBI keep an eye on him.
When the FBI interviewed Mateen — for his third time — in July, he said he recognized Abussalha from the mosque but was not an acquaintance. When pressed about the radical videos, the security guard denied having watched them.
And with that, the FBI moved on to other potential threats.
del.wilber@latimes.com
Twitter: @delwilber
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