BOSTON - Plucking a couple of faces in baseball caps out of a swarming crowd, the FBI zeroed in on two suspects in the Boston Marathon bombing and shared surveillance-camera images of them with the world Thursday in hopes the public will help hunt them down.
The somewhat blurry but still detailed photos and video depict one young man in a dark cap and another in a white cap worn backward, both wearing backpacks and one walking behind the other on the sidewalk near the finish line as marathoners run by.
The man in the white hat was seen setting down a backpack at the site of the second explosion, said Richard DesLauriers, FBI agent in charge in Boston.
This combination of images released by the FBI on Thursday, show two images taken from surveillance video of who the FBI are calling suspect number 2, left, in white cap, and suspect number 1, right, in black cap, as they walk near each other through the crowd before the explosions at the Boston Marathon on Monday.
"Somebody out there knows these individuals as friends, neighbors, co-workers or family members of the suspects," he said. "Though it may be difficult, the nation is counting on those with information to come forward and provide it to us."
They looked much like typical college students, but DesLauriers described them as armed and extremely dangerous, and urged anyone who sees or knows them to tell law enforcement and "do not take any action on your own."
The break in the investigation came just three days after the attack that killed three people, tore off limbs and raised the specter of another terrorist attack on U.S. soil. FBI photo-analysis specialists have been analyzing a mountain of surveillance footage and amateur pictures and video for clues to who carried out the attack and why.
The volume of information is likely to grow, joined now by a torrent of tips from people who think they might know the suspects. In releasing the images, the FBI gambled that useful clues will emerge, not just time-wasting leads.
Authorities are selective in putting out images of suspects because doing so risks tipping off the hunted and losing the element of surprise. But it can be a last resort when authorities hit a wall trying to identify or capture someone.