A reward of up to $10,000 has been offered for information leading to the arrest of the man suspected of robbing a Somerville bank on Wednesday.

The FBI Boston Violent Crimes Task Force and the Somerville Police Department announced the offer for a reward on Thursday, more than a day after the robbery took place. The suspect, an unidentified man in his 30s, is considered armed and dangerous.

The armed robbery took place at the Middlesex Federal Savings Bank in Davis Square at around 10 a.m Wednesday. The man fired multiple rounds with a black revolver upon entering the bank. After robbing the bank, he exchanged gunfire with a responding city officer before fleeing on foot. The officer was not injured.

Police describe the suspect as a light-skinned male, between 5'7" and 5'11" and weighing about 175 pounds with a medium build. At the time of the robbery, he was wearing a hooded camouflage jacket with a Nike logo, a blue beanie, blue jeans and black sneakers.

The police held one person in custody on Wednesday, but determined he was not the suspect.

As of 11:30 a.m. Wednesday, police had set up a staging area at Powder House Circle, and at least a dozen police were on-hand, with about half in swat gear.

As the suspect fled the scene, surveillance footage shows, a bystander knocked into him in an attempt to slow him down.

The bystander, Dave Powers, a web developer from Somerville, was headed to work this morning when a man came running at him just outside the Davis T station. In the moment, Powers had no way of knowing that the man was armed and had just robbed a bank. But he knew something was amiss, and reached out to shove the man as he attempted to pass by.

"I could tell he was in pursuit by a police officer, so I was in position to react and had enough time to do so, so I did," Powers said. "[I was] just hoping to slow him down so he could be apprehended by the officer."

Despite being slowed, the suspect managed to escaped on foot. The collision with Powers knocked both a bag of cash and a gun away from the fleeing suspect.

Powers demurred when asked if he felt like a hero, and said until he saw surveillance video of the incident, he could barely believe what had happened.

This is a developing story and will be updated.