First BART officer ever killed in line of duty identified DUBLIN, Calif. -- Investigators are working to determine the circumstances that led a Bay Area Rapid Transit police officer to accidentally shoot and kill a fellow officer, the first on-duty fatality in the department's 42-year history, authorities said. A statement from California Gov. Jerry Brown received early Wednesday identified BART Sgt. Tom Smith, 42, of San Ramon, as the officer shot Tuesday afternoon. Smith, a detective who's been with the department for 20 years, is survived by his wife and 6-year-old daughter, Brown said. "Sergeant Smith's family, friends and colleagues are in our thoughts as we honor his service during this painful time," the statement said. Smith, 42, comes from a law enforcement family, reports CBS San Francisco station KPIX-TV. His wife is a K-9 officer with BART police and Smith's two brothers are officers at two other Bay Area agencies. Smith also behind a young daughter. The officers - members of BART's detective unit - were conducting a probation search at an apartment in the East Bay city of Dublin. The governor said the officers were serving a warrant regarding several robberies on BART property. The suspect, whose name has not been released, was not home at the time. Sgt. J.D. Nelson of the Alameda County Sheriff's Office, which will investigate the shooting, told the Contra Costa Times that officers knocked before entering the unlocked apartment with their guns drawn. Details about what happened next haven't been released, but KPIX quotes Nelson as saying the other officer accidentally fired a shot that wounded Smith. Smith was taken to Eden Medical Center in Castro Valley, where he died from his injuries. Television reports showed lines of officers outside the hospital saluting as their fallen comrade's body, draped in a large American flag, was loaded into a coroner's van. BART Police Chief Kenton Rainey didn't answer any questions from reporters at a brief news conference Tuesday evening. "We ask that everyone please give us a chance to catch our breath" and to grieve, he said. "The entire BART organization is deeply saddened by this tragic event, and we ask the public to keep the officer's family in its thoughts and prayers," Rainey and BART General Manager Grace Crunican said earlier in a joint statement. They said they were withholding other details for now. The name of the officer who fired his gun hasn't been released. BART has had its share of troubles in the past. Among them was the fatal shooting on New Year's Day 2009 of Oscar Grant III, an unarmed black BART passenger who had been detained at the Fruitvale station after reports of a fight.