The Search Begins
The manhunt began even before the smoke cleared. The FAA shut down the airspace around the scene, and police using bullhorns told drivers to evacuate the city. Officials blocked cell-phone service in the area to prevent any other devices’ being detonated remotely, which made it hard for athletes and spectators to let their families know they were safe. (Google, which has its own crisis-response team, launched a Person Finder to help friends and families reconnect.) SWAT teams converged to patrol hospital perimeters in the event there were more devices hidden. Many people dropped their backpacks and bags as they fled, and police had to treat each one as a suspicious package.
On Boston Common, squadrons of men in fatigues and berets lined up in formation with assault rifles on their shoulders as helicopters swarmed overhead and armored Humvees idled nearby. Forensic teams working for the Joint Terrorism Task Force sealed off a 15-block radius and began scouring the wreckage for pieces of the devices. All of the shrapnel and components—including those recovered by doctors from victims—was collected and sent to the FBI’s laboratory in Quantico, Va., where experts began reconstructing the bombs.
In his initial remarks Monday evening, President Obama was so subdued as to sound perfunctory as he promised to “get to the bottom of this.” He avoided the word terror, since no one knew yet if this was political violence, whether foreign or domestic, or something equally lethal but differently sourced. By the next day he was back at the podium, deploring the “heinous and cowardly act” and using variations of the word terror four times in less than a minute. He honored the heroism of all the first responders and the residents of Boston. “If you want to know who we are, who America is, how we respond to evil, that’s it,” he said. “Selflessly, compassionately, unafraid.”
The U.S. intelligence apparatus has more and mightier tools with which to track terrorists than before the great rewiring that followed 9/11. Since pressure-cooker bombs can be detonated by cell phones, officials could track every call made through the closest cell towers around the time of the blast. Unlike after past attacks, this time investigators were quick to crowdsource the manhunt. Police set up a tip line and within 24 hours had received more than 2,000 tips. This was a crime with a million witnesses: police asked for spectators’ photos and videos and collected surveillance tapes from area businesses to scour each frame for clues. “There has to be hundreds, if not thousands, of photographs, videos and other observations that were made down at that finish line yesterday,” said Timothy Alben, superintendent of the Massachusetts state police. “You might not think it’s significant, but it might have some value to this investigation.” Experts planned to study “every frame of every video that we have to determine exactly who was in the area,” said Boston police commissioner Edward Davis, and use facial-recognition software to compare the faces of any suspects against passport and visa photos and other databases.
The FBI and CIA scoured their intelligence databases for missed signs that the attacks had been imminent. And national signals intelligence assets had “ears up” for any congratulatory chatter by terrorist organizations thought to be planning attacks against the U.S. But the discovery that it was a pressure-cooker bomb was the first big break. Back in 2004, Homeland Security was worried enough to issue an alert: “A technique commonly taught in Afghan terrorist training camps is the use/conversion of pressure cookers into IEDs,” the bulletin warned. The materials were easy to find and assemble, and the device could be detonated by “digital watches, garage door openers, cell phones or pagers.” Al-Qaeda’s English-language magazine Inspire ran a story in 2010 called “Make a Bomb in the Kitchen of Your Mom,” which recommended pressure cookers as explosive devices. A 2010 suicide bomber in Stockholm had rigged a pressure-cooker bomb that failed to detonate fully; it killed only the bomber. And the failed 2010 SUV bomb in New York City’s Times Square was a pressure-cooker device featuring 120 firecrackers.
This story is part of TIME’s Boston bombing special tablet edition, available on iPad, Nook, Android and Kindle