"We’re offering a reward up to $10K," the FBI's Boston office said in a tweet Thursday. "Call 857-386-2000 or email http://tips.fbi.gov."
The suspect, an as-yet-unidentified Hispanic man, robbed the Middlesex Federal Savings Bank in Davis Square around 9:57 a.m. Wednesday.
In a release with more photos and video, the FBI said he fired a shot into the ceiling, demanded money, and then exchanged gunfire with a Somerville Police officer who tried to interrupt the robbery.
During the robbery, he was wearing a hooded camoflage jacket with the Nike logo on it, a blue beanie, a dark glove on his left hand, blue jeans, black sneakers, and a black and red backpack.
A Good Samaritan tried to stop the man. Surveillance video from a nearby business shows the bystander knocking a the backpack out of the suspect's hands as he ran from police.
Inside that backpack was a handgun, but Somerville Police believe the man may still be armed.
Despite a thorough door-to-door search in which heavily-armed SWAT teams searched nearby homes, offices, and rooftops, the man was not caught.