An FBI agent who was killed as agents closed in on three bank robbery suspects may have been accidentally shot by a colleague, the agency said.

Special Agent Barry Lee Bush, assigned to the FBI's Newark office, died Thursday after his stakeout team shot at the three armed men, who were in vehicles outside a PNC Bank branch. The FBI said the suspects never fired their weapons. Two were quickly arrested, and hundreds of agents were searching the area for the third man on Friday.

"Preliminarily, information suggests the agent may have been fatally wounded as a result of the accidental discharge of another agent's weapon during a dynamic arrest situation," the FBI said in a statement Thursday night.

Pedro Ruiz, special agent in charge of the FBI's Newark office, said the suspects did not fire their weapons, which included two assault rifles and a handgun. He said he did not yet know how many shots were fired and would not elaborate on what led the agents to shoot.

Bush, 52, and his team were tracking a group of men believed to be responsible for at least four bank robberies, the FBI said. In two of them, the suspects had fired assault weapons while inside the bank, the agency said.

The men arrested outside the Readington bank in north-central New Jersey were identified as Wilfredo Berrios, 28, and Michael Cruz, 21, both of New Brunswick. Officials said the third man escaped on foot.

About 300 law enforcement officers were searching for the fugitive, focusing on a 2-square-mile wooded area near the Fox Hollow Golf Club. He was identified by state police as Francisco Herrera-Genao, 22, also of New Brunswick.

Berrios and Cruz were to be charged with attempted armed robbery of the Readington bank, the U.S. Attorney's Office in Newark said.

It was not immediately clear if the men had attorneys who could comment. Telephone listings for the men could not be located.

The FBI had started investigating Berrios, Cruz and Herrera-Genao after a March 2 bank robbery. A surveillance camera at a shopping center caught the masked gunmen abandoning a stolen Honda they had used in the robbery and getting into their "switch car," a rental vehicle that was traced to Berrios, according to the criminal complaint released by the U.S. Attorney's Office.

After his arrest, Cruz said the men were preparing to rob the Readington bank, according to the complaint. Cruz also said he, Berrios, Herrera-Genao and Efrain Lynn, 21, of New Brunswick, had robbed a bank in South Brunswick on March 16, the complaint said.

Lynn was arrested Thursday on a warrant unrelated to the bank robberies, federal prosecutors said.

Witnesses in Readington described a chaotic scene as the gunfire broke out Thursday.

Brian Agans, who works in an engine shop across from the bank, said he heard a "pop, pop, pop." He ran outside to make sure a mechanic wasn't having a problem with equipment, but instead saw law enforcement swarming.

"All hell was breaking loose. I've never seen so many police and authorities take action ever in my life," he said.

Bush joined the FBI in August of 1987, serving in Kansas City and transferring to Newark in 1991. He is survived by a wife and two grown children, the FBI said.