A transit worker opened fire at a rail yard in San Jose, Calif., early Wednesday, killing eight people, many of them fellow employees, according to the Santa Clara County Sheriff’s Office, which reported that the gunman was also dead.

California law enforcement officials identified the gunman as Samuel James Cassidy, 57, a maintenance worker who had been with the V.T.A. for at least a decade and whose suburban home was in flames as the shooting started.

The attack — which occurred as dispatchers and maintenance workers at the Santa Clara Valley Transportation Authority were preparing for the start of the day’s service — spread turmoil through the sprawling municipal complex near downtown San Jose, the nation’s 10th-largest city and the heart of Silicon Valley.

Buildings were evacuated, and light rail service was gradually shut down as bomb squad teams scoured the area for explosives. Employees who had been working the busy morning shift were led to a separate building, where family members awaited.

Gov. Gavin Newsom of California met with some of them. In an afternoon news conference, he praised sheriff’s deputies for their response to the shooting and lamented yet another American tragedy. “What the hell is wrong with us,” he said, “and when are we going to come to grips with this?”