Officials on Monday identified a bus driver and the man suspected of fatally shooting him in West Holllywood over the weekend in what is believed to be the first on-duty murder of an operator in the transit agency's history.

Anthony Chambers, 41, of Los Angeles, was booked late Sunday for investigation of murder and remained held on $1 million bail, sheriff's investigators said. It wasn't immediately known if he had retained an attorney.

No motive has been given for the shooting, which happened early Sunday when Chambers and the bus driver were believed to be the only people on the Metropolitan Transportation Authority bus. The shooting occurred just blocks from the route of the Amgen Tour of California bicycle race.

Rick Jager, a spokesman for the Los Angeles County transit agency, identified the driver as Alan Thomas, 51, of Los Angeles. Thomas, who was married, worked for MTA for five years, Jager said.

MTA officials said they can't recall another murder of an on-duty driver in the agency's nearly 20-year history or with its predecessor, Southern California Rapid Transit District.

The bus was equipped with video cameras but it was unclear if they recorded the incident.

The vehicle, which was on its regular run through a neighborhood on the busy Santa Monica Boulevard, appeared to have stopped alongside a curb just before Thomas was attacked, authorities said.

Witnesses told investigators they saw Chambers climb out a window and run down the street. He was arrested soon after.

Two firearms were recovered and a suspicious package was found on the bus but it wasn't determined to be an explosive device, authorities said.

A makeshift memorial of candles and flowers has been left at the shooting site and grief counselors were available for MTA employees.

MTA drivers are given training to deal with unruly passengers or potentially violent situations, Jager said.

"They are trained to either to diffuse it or call in," he said. "Don't aggravate it or escalate it. This is an absolutely unfortunate situation."