At 2:49 p.m. on Monday, April 15, 2013, as a sea of spectators cheered the runners completing the Boston Marathon, two bombs exploded about 12 seconds and 183 yards apart, on the north side of Boylston Street. It was an act of terror that took the lives of three people and injured at least 264 others, and plunged an entire city into a miasma of fear.
But that moment also signaled the beginning of a second, even more grueling marathon, in which an army of FBI agents and local police raced to identify and capture the perpetrators of the horrific crime, before they could escape or perhaps even strike again.
That second marathon would end four days and six hours later, with one suspect dead and the other in custody, and Boston’s population breathing a collective sigh of relief.
But to get to that finish line, investigators had to stage what might be the most remarkable manhunt in law enforcement history. They were forced to start from square one, without likely suspects or an apparent motive, and sift through the carnage, the recollections of witnesses, and vast amounts of video and still photos in the search for clues.
By 4 p.m., just over an hour after the explosions, a team that included Boston Police Commissioner Ed Davis, Richard DesLauriers, Special Agent in Charge of the FBI’s Boston office, and officials from other law enforcement agencies had set up a command post at the Westin Copley Place hotel. Eventually, more than 20 different agencies would join in the effort, and the hotel’s third and fourth floors would serve as the base for more than 1,000 investigators.
One of the first moves was to gather as much video footage and photographic evidence as they could, starting with news media clips and footage from surveillance cameras from the approximately 200 businesses in the vicinity of the blast. Additionally, the team appealed to marathon spectators to email pictures they had taken with phones.
A surge of photos and video of the event uploaded to Twitter, Facebook, Vine, YouTube and other social media provided still more potential information. In the first 24 hours, the team compiled an astonishing 10 terabytes of data, according to FCW.com, a website that covers federal information technology. That’s roughly enough to completely fill the hard drives of 10 high-end laptop computers.
Meanwhile, chemists, explosives experts and crime scene analysts—including more than 30 staffers from the Federal Bureau of Alcohol, Tobacco and Firearms, converged upon the 15-block zone in the vicinity of the blast. They perused thousands of pieces of potential evidence.
On the roof of a local hotel, they found the lid from a pressure cooker—a clue that the bombers had used the cooking implement to construct a homemade bomb—and on the street, recovered ball bearings that had been inside the explosive devices.
According to court documents, the FBI knew that a design for such a bomb had been published by the terrorist organization al-Qaeda on the Internet in 2010, and figured that the bombers had gotten the instructions there.
Shreds of black nylon found with the bomb parts convinced the investigators that the two bombs had been placed in backpacks.
Back at the command post and at an FBI lab in Virginia other investigators sifted through the mountain of visual data they were amassing, which eventually amounted to 120,000 still photos and nearly 13,000 video clips.
They searched for anything unusual—people pacing back and forth anxiously, for example, or carrying bags that might possibly contain explosive devices. One agent alone reportedly watched the same segment of video more than 400 times.
Eventually, one of the investigators spotted a backpack-carrying man in a white hat talking on a cell phone. As the crowd around him reacted to the first explosion, he remained calm, and then walked away without his backpack—about 10 seconds before the second explosion.
It was the first glimpse of one of the bombers. “It brought tears to our eyes each time we watched it,” DesLauriers later recalled.
But it was a thin lead. The image was extremely grainy, so that it was impossible to identify the suspect from it. Investigators now knew that he’d made a cell phone call at a certain time, but in that densely-packed area, so had probably hundreds of thousands of other people.
Soon, however, investigators happened upon a second piece of security camera video, shot about 12 minutes before the explosions, which showed the man in the white hat walking with another, bigger man, who wore a black hat and sunglasses and carried a similar backpack. They were headed in the direction of the blast site.
One of the men in the video matched the description given by bombing victim Jeffrey Bauman, who told FBI agents that just before the blast, he’d seen a man in sunglasses and a black cap place a backpack on the ground and step away.
Though the FBI possessed facial recognition software, the images of the suspects captured on street surveillance videos were too grainy to match their faces against the pictures in government databases.
By Thursday morning, the law enforcement team was debating what to do. Many of the brass from the FBI and other law enforcement agencies wanted to hold off releasing the photos, in the belief that another 12 to 24 hours of analyzing phone records might point them to a suspect. But they also feared that the bombers might strike again. “We did not want to have more bombs go off in Boston or anywhere else, and the quickest way that we could identify these individuals was to share that video evidence with the American public,” DesLauriers later explained.
At approximately 5:00 p.m. on Thursday evening, the FBI posted photos of the suspects on its website. “Somebody out there knows these individuals as friends, neighbors, co-workers or family members of the suspects,” DesLauriers explained to reporters. “Though it may be difficult, the nation is counting on those with information to come forward.”
Indeed, the suspects’ anonymity soon vanished. One of them soon received a copy of one of the FBI’s images via Twitter, from someone who noted the resemblance.
Thursday evening, just outside Boston in Cambridge, the two suspects allegedly ambushed and shot to death Sean Collier, a Massachusetts Institute of Technology campus police officer, apparently in a vain effort to steal a second firearm from him, and then carjacked a black Mercedes-Benz SUV belonging to a 26-year-old man from China. After being held captive for over an hour, the victim managed to get away at a gas station and call 911.
In the early morning hours of Friday, in the nearby community of Watertown, a local police officer made a visual ID on the carjacked vehicle, and a violent shootout ensued between the two suspects and police. Officers managed to tackle and handcuff one of the suspects in the street—only to see him run over by the SUV driven by the other, smaller man, who managed to escape.
The suspect who’d been run over soon died from his injuries, before investigators could talk to him. But at the hospital, FBI agents brought in an electronic device that scanned his fingerprints and ran them through the agency’s database, and attempted to identify a match. Soon, they had a name: Tamerlan Tsarnaev, 26, an immigrant from Kyrgyzstan who’d arrived in the U.S. in 2003. The dead man had been interviewed by the FBI in 2011, because of a tip from the Russian government that he might have connections to Chechen extremists.
Searches of other databases yielded his younger brother Dzhokhar Tsarnaev, 19, who unlike Tamerlan had become a naturalized citizen. The FBI’s facial recognition expert visually compared the Dzhokhar’s driver’s license photo with the “white hat” image, and concluded they likely were the same person.
Police soon found the vehicle in which the younger Tsarnaev had escaped, abandoned in Watertown. They called residents in the neighborhood and advised them to remain in their homes while authorities searched for the suspected terrorist. As the sun rose on Friday morning, however, Dzhokhar Tsarnaev still had not been found, and Massachusetts Governor Deval Patrick made the decision to extend the lockdown to the entire city of Boston.
That evening, a tactical team surrounded the surviving suspect, who had taken refuge in a boat parked in a Watertown resident’s backyard, and he was taken into custody.
The search was over.
