Records offer rare glimpse into Boston Marathon bombings inquiry

Within 48 hours of the Boston Marathon bombings, federal law enforcement officials had chased down more than 1,400 leads in the frantic race to learn who killed three people and injured more than 260 others, according to law enforcement records obtained by The Times.

Agents swarmed local gun shops, fireworks stands and a Barneys New York department store, tracking down clues. Law enforcement officers poured in from Maine, New Hampshire and Maryland as leads were pursued as far away as Dallas, Kansas City and Perris, Calif.

Bomb shards were rushed to the FBI lab in Virginia, which identified the explosive devices as pressure-cooker bombs.

Two dozen pages of Justice Department documents, including investigation reports and case logs, reveal the chaotic early days of the federal inquiry and the intense pressure to make an arrest.

After some dead-ends and wrong turns, including an initial focus on a single suspect, investigators ultimately concluded that two brothers, Tamerlan and Dzhokhar Tsarnaev, carried out the April 15, 2013, attacks.

The documents provide a rare glimpse into an investigation that has been kept unusually secretive.

Documents show that two days after the attack, agents had scanned extensive surveillance videos along Boston’s Boylston Street, viewed dozens of private video clips and pulled mobile phone records from throughout downtown Boston.

In total, the FBI crime scene stretched for 15 city blocks, covering the rooftops and top floors of high-rise buildings along the marathon route. In three days, agents had mapped the entire area, with much of the evidence already collected, stamped and sorted, documents show.

“Extensive private security video, news media video, private citizen video and DHS [Department of Homeland Security] City Wide security system video exist of the entire area where the bombings took place,” the documents state.

“Dozens of [terabytes] of high-definition video have been obtained by multiple agency digital recovery teams and are being reviewed by multi-agency teams at the FBI command post…. Cellphone records in that area for that time have been isolated and screened down to a very manageable number to work on.”

Not all of the leads paid off. Early on, investigators zeroed in on a suspect they believed acted alone.

“The investigation is evolving rapidly with very promising leads,” a top federal law enforcement supervisor wrote on the second day of the investigation, raising hopes that a break in the case was near. “Preliminary images of a believed suspect have been identified carrying and placing both devices as well as talking on a cellphone.”

Investigators also considered but quickly dismissed media reports claiming a pair of Middle Eastern-looking men were responsible. “Initial leads based on public reporting regarding 2 to 3 males of Middle Eastern descent being involved were ruled out,” the records state.

Inside the FBI’s eighth-floor command post, the bureau was fielding new bomb threats while also trying to keep its work secret.

The initial lead about a single bomber was so sensitive that a top official wrote, “No specific information concerning the device or the suspect will be placed in this [report] due to ongoing operational security concerns related to information leaks.”

But soon investigators had turned their sights to the Tsarnaev brothers, Chechen immigrants from Russia. Tamerlan was a legal U.S. resident, and Dzhokhar is a naturalized American citizen.

In a federal indictment in Boston, the brothers are described as separately placing black backpacks on the ground, chatting with each other on cellphones, and then separately igniting the explosives.

To learn more about the brothers, agents entered local mosques for details about the Tsarnaevs’ radical ideology. They went to Barneys New York at the Copley Mall in Boston and retrieved video footage of a man resembling Dzhokhar Tsarnaev. A federal air marshal in Chelsea, Mass., was interviewed. Records of jail calls to a Middlesex County, Mass., inmate were scrutinized.

Musa Khadzhimuratov, a Chechen refugee and Tamerlan Tsarnaev acquaintance, was questioned about a missing firearm. The apartment of Khadzhimuratov, who was considered an early “target” in the investigation, was searched in Manchester, N.H., where Tamerlan Tsarnaev reportedly bought fireworks and practiced at a shooting range.

The documents, as well as newly obtained Portland, Maine, police records, also provided new details about the Portland drug ring that federal agents suspect Tamerlan Tsarnaev used to finance the attack.

A 9-millimeter Ruger that he fired at police was once owned by Biniam “Icy” Tsegai, 26, of Portland. In the new documents, Tsegai is described as a “higher-up” in the Portland drug gang who was arrested May 23, 2013, on suspicion of trafficking cocaine out of Massachusetts.

It remains unclear how the firearm went from Tsegai to Tsarnaev. But according to the documents, Tsegai, an immigrant from Sudan, “denied possessing firearms and denied participating in the transfer of firearms to individuals from the Boston area or Massachusetts.”

In May 2014, he pleaded guilty to conspiring to possess and distribute crack cocaine.

Additional details about the investigation may emerge when Dzhokhar Tsarnaev’s federal trial begins this year, though defense attorneys are seeking a delay.

Some aspects may never be known. Tamerlan Tsarnaev, considered by many to be the leader of the bomb conspiracy, was slain as police attempted to capture him that first week after the attack.

An associate, Ibragim Todashev, was killed by an FBI agent in Florida a month after the bombings. Todashev allegedly tried to attack the agent while being interviewed.

Dzhokhar Tsarnaev, the sole defendant in federal court, has pleaded not guilty.

Well over a third of the 550 filings and judicial orders are sealed in his case. One example is this filing from Sept. 2, titled: “Sealed reply to Sealed response to Sealed Motion by Dzhokhar A. Tsarnaev re SEALED MOTION.”

richard.serrano@latimes.com

Twitter: @RickSerranoLAT