Last night’s violence erupted hours after the FBI released video and photographs showing the two suspects and called for the public to help identify them. They said one of the men — the one shown in a white cap who is still on the loose — was caught on camera setting down a black backpack at the site of the second explosion just minutes before the bomb went off. The images were posted to the FBI’s website, which was temporarily knocked offline as it was reportedly hit with its highest level of traffic ever.