05/21/2012 12:25 pm ET Updated May 23, 2012

Alan Thomas, MTA Bus Driver, Shot Dead: Anthony Chambers Arrested (VIDEO)

Friends, family and the MTA community are mourning the loss of Alan Thomas, a 51-year-old Metro bus driver shot dead on the job Sunday morning in West Hollywood.

Thomas was driving the route 105 bus east on Santa Monica Boulevard near La Cienega Boulevard when a passenger shot him in the chest after 9 a.m., reports KABC.

A bus supervisor who happened to be in the area for the Amgen Tour of California bicycle race saw the bus drift backward, hitting another vehicle, reports CBS2/KCAL9. When the supervisor boarded the bus, he found Thomas injured.

Thomas was taken to Cedars-Sinai, but he died of his wound at approximately 9:30 a.m. He had worked for LA Metro for five years.

"It's a tragedy, everybody at MTA feels horrible about it," Metro's Chief Executive Officer Art Leahy said to the Los Angeles Times. "It's the first time I've ever known this to happen in my career here. ... It's terrible." Leahy also told press that he couldn't recall a fatal shooting of a bus driver for either LA Metro or the Southern California Rapid Transit District.

Authorities arrested 41-year-old Anthony Craig Chambers, believed to be the only passenger on the bus, after witnesses saw him climb out of the bus window and run down the street. He was booked at the West Hollywood Sheriff's Office and is being held on $1 million bail.

Investigators were able to recover two firearms and found a suspicious package on the bus, reports the Associated Press. The package was determined not to be a threat.

A vigil is planned Monday at 8 p.m. at Metro Division 7, reports KTLA. Hundreds are expected to attend.

CORRECTION: A previous version of this story misspelled Alan Thomas' name. We regret the error.