The images show two men, both wearing baseball caps. In one image, the pair appear to be walking together, one behind the other, down a sidewalk on Boylston Street, in the direction of the race's finish line. According to the FBI, the suspect in white hat set down a backpack at the site of the second explosion, just in front of a restaurant named Forum. (The suspect in the black hat was not observed setting anything down.) Inside the backpack, officials believe, was an explosive device. Within minutes of the backpack being set down, it went off.
But despite this break in the case, investigators still have no names for the pair. Hence the release of the images. At a press conference, Richard DesLauriers, the special agent in charge of the FBI's Boston field office, urged anyone with any information at all about the two suspects to contact the FBI.
"Somebody out there knows these individuals as friends, neighbors, co-workers, or family members of the suspects," DesLauriers said. "Though it may be difficult, the nation is counting on those with information to come forward and provide it to us."
The FBI is particularly interested in speaking with anyone who was at Forum on the day of race.
According to DesLauriers, the suspects should be considered armed and extremely dangerous. He emphasized that no one except law enforcement should try to approach or apprehend the two men.
Following DesLauriers' prepared statement, a reporter asked if investigators knew what the suspects did after the explosions.
"Suspect number two with the white [hat] on proceeded west on Boylston Street," DesLauriers said. "And that's all we know right now."