Latin Night was wrapping up at Pulse around 2 a.m. as about 320 people danced and drank to thumping reggaeton, salsa and merengue.
Minutes later partyers were fleeing into the street. Some clutched gunshot wounds. Others were splattered with the blood of people they didn't know. Some were carried and dragged to safety. Police frantically loaded one injured man into the bed of a pickup truck.
Those still trapped in the gay nightclub could only hide.
Before the sun rose in the humid Florida air Sunday, 50 people lay dead, and 53 more were injured – the deadliest shooting in American history.
The gunman, 29-year-old Omar Mateen, died in a shootout with SWAT officers three hours after his rampage began. Mateen, the son of Afghan immigrants, called 911 during the siege, pledging his allegiance to Islamic State and mentioning the Boston Marathon bombing in 2013.
The FBI had twice investigated Mateen on suspicion of having terrorist ties in 2013 and 2014, yet they could not find conclusive evidence. Mateen was able to legally purchase a handgun and a .223 AR-15-style assault rifle days before the massacre.
After the shooting, a statement attributed to Islamic State's Amaq news agency said the attack "was carried out by an Islamic State fighter."
National security officials said they had not determined whether he was directed by Islamic State or simply inspired by the group. Nor had they learned how other motivations, such as homophobia, factored into the attack.
"We know enough to say that this was an act of terror and an act of hate," said President Obama at a White House media briefing after meeting with the FBI director. "And as Americans we are united in grief, in outrage and in resolve to defend our people."
"This massacre is therefore a further reminder of how easy it is for someone to get their hands on a weapon that lets them shoot people in a school or in a house of worship or a movie theater or in a nightclub. And we have to decide if that's the kind of country we want to be. And to actively do nothing is a decision as well," he said.
The top Democrat on the House Intelligence Committee, Rep. Adam B. Schiff (D-Burbank), noted similarities to the November attack on the Bataclan nightclub in Paris and said in a statement that intelligence officers were combing through terrorism databases to see whether there were any known links between the shooter and a terrorist group.
FBI agents were interviewing Mateen's family and friends Sunday and planned to search his home, authorities said.
Since 2014, Islamic State has urged supporters in the U.S. to plan and carry out deadly attacks without traveling overseas first or communicating directly with the group's leaders. Such so-called lone -wolf attacks are difficult to prevent because there are few communications to uncover or visits to terrorist training camps to track.
In May, Islamic State renewed a call for supporters in Europe and the U.S. to launch attacks on civilians during the holy month of Ramadan, which lasts from early June to the beginning of July.
"Ramadan has come near, and it is the month of raids and jihad, the month of conquest," Abu Muhammad Adnani, an Islamic State spokesman said in an audio message posted online.
Make it "a month of suffering" for non-Muslims, Adnani added, saying the message was specifically directed to "soldiers and supporters" in Europe and America.
Whether Mateen heeded the call or followed his own agenda is unclear.
From his home in Fort Pierce, a sleepy town on the Atlantic coast, Mateen drove 120 miles to Orlando. He was a man brimming with rage. He beat his ex-wife for not doing the laundry, for any perceived slight; she thought he was mentally ill and left him after four months of marriage. At the security firm where he worked, he vented his hatred for gays, blacks, women, Jews. He grew furious on a recent trip to Miami, where he saw two men kissing in a park.
Mateen pulled into the parking lot at Pulse in the early hours of Sunday. The club sits on a humble commercial strip of South Orange Avenue, next to Dunkin' Donuts, across from a RadioShack.
At the entrance, an armed security guard confronted Mateen at 2:02 a.m. Shots were fired, but whatever happened did not stop Mateen. He stormed into the club just as last call was announced over the microphone.
When the first of dozens of shots rang out, many thought the sound was part of the music.
When one of the clubgoers, Chris Hansen, heard the loud banging noises, he thought the pops seemed to move with the beat.
"I thought it was a Ying Yang Twins song or something," Hansen recalled.
But the DJ turned down the sound and the sharp pop of gunfire became chillingly clear. In cellphone videos, the sound of single, high-velocity shots echoed through the streets. At other times, bullets crackled like firecrackers, the sound of a fully automatic weapon.
Partyers ran for the doors and fled into the surrounding neighborhood. Some had gunshot wounds.
At 2:09, the club posted a chilling note on its Facebook page: "Everyone get out of pulse and keep running."
But many couldn't escape. They barricaded themselves in the bathrooms. One woman covered herself with dead bodies to hide from the shooter. Two others briefly hid under the DJ stand.
Many who couldn't get out texted their loved ones.
"Mommy I love you," wrote one man, identified by the Associated Press as Eddie Justice, to his mother, Mina Justice.
"In club they shooting"
"I'm gonna die"
"He's in the bathroom with us"
The fate of Justice, 30, was unknown.
[Update: Authorities have confirmed Justice was among those killed.]
Mateen stopped shooting and made his call to 911 about 20 minutes into the attack. He held the remaining 30 clubgoers as hostages. Authorities said they did communicate with him at this point, but did not specify what was said.
Outside, dozens of emergency vehicles poured into the area. There were not enough ambulances, so police cars transported many of the wounded to the hospital. The Orlando Fire Department called its bomb squad and hazardous material team to the scene after 3 a.m.
At 5:05 a.m., a SWAT team made up of 14 Orlando police officers and Orange County sheriff's deputies moved in to rescue the 30 hostages. They busted through a wall in an armored vehicle.
A fierce shootout broke out when they located Mateen. One officer took a shot to the head but was saved by his Kevlar helmet.
At 5:53 a.m., Mateen was dead.
No one left more carnage behind in an American shooting. Not the Columbine High School shooters in Colorado, where 13 people died in 1999; not Adam Lanza in Newtown, Conn., where 26 people were killed in 2012; not Seung-Hui Cho at Virginia Tech in Blacksburg, Va., where 32 people were killed in 2007.
Muslim leaders in America, bracing for a backlash, condemned both the slaughter and Islamic State.
"You do not speak for us," said Nihad Awad, executive director of the Council on American-Islamic Relations. "You do not represent us. You are an aberration. You are an outlaw. You don't speak for our faith. "
He continued, railing against the extremists: "They never belong in this beautiful faith. They claim to. But 1.7 billion people are united in rejecting their extremism, interpretation and their acts and senseless violence."
Brandon Wolf escaped the Orlando massacre by hiding in the bathroom. But he couldn't find his friend Drew.
"Please Drew. Please," he tweeted at 6:39 a.m.
He braced himself for the worst.
"Lord give me strength," he wrote.
Then Wolf heard news he didn't expect: His other friend Juan was among those killed in the attack.
Devastated, he grieved and waited for word of Drew.
More than 15 hours after the attack, he tweeted again: "I want to thank you for all your prayers. And thoughts. But we lost them both. 2day is a sad day for earth and an incredible day for heaven."
At an Orlando hospital, Shawn Roysten, who survived the shooting, waited at the side of friends who fared less well, including one who was shot five times.
Roysten, a New York resident in town to visit family, had gone to the club as part of its Latin night. He arrived about 12:30 a.m. When the gunfire started, Roysten ran out and hid behind a fence, said his mother, Helene.
The bullets just kept coming, penetrating the fence. "There were so many bodies, so much blood," Roysten told his mother.
Mozingo and Pearce reported from Los Angeles and Wilkinson from Orlando. Contributing to this report was the staff of the Orlando Sentinel; Times staff writers Brian Bennett and Del Quentin Wilber in Washington, Sarah Parvini in Los Angeles and Molly Hennessy-Fiske in Orlando; and the Associated Press.
June 13, 1:30 a.m: This article has been updated with a report confirming that Eddie Justice was among those killed.
June 12, 9:42 p.m.: This article has been updated throughout with additional details and background.
8:53 p.m.: This article has been updated throughout with additional details and background.
5:59 p.m.: This article has been updated with comments from Omar Mateen's ex-wife and additional details on wounded and the FBI investigation.
2:13 p.m.: This article has been updated with reports that the gunman had previously been investigated for terror ties and that the guns were purchased legally.
12:12 p.m.: This article has been updated with a report that Islamic State is claiming the gunman was a fighter for the group, and with additional remarks by President Obama.
11:06 a.m.: This article has been throughout with additional details and background.
8:09 a.m.: This article has been throughout with additional details and background, including an updated death toll.
6:50 a.m.: This article has been updated with a preliminary identification of the gunman.
4:37 a.m.: This article has been updated with a revised death toll.
4:18 a.m.: This article has been updated with reports of multiple deaths.
3:38 a.m.: This article has been updated with comments from witnesses.
3:20 a.m.: This article has been updated with police reporting a "mass casualty situation."
3:01 a.m.: This article has been updated with police reporting the gunman is dead.
2:16 a.m.: This article has been updated with witness quotes.
1:51 a.m.: This article has been updated with a police department update.
1:47 a.m.: This article has been updated with witness quotes.
1:36 a.m.: This article has been updated with a report a bomb squad as been called in.