A former Northern California transit officer has broken down and cried on the witness stand while describing how he shot and killed a man on a train station platform more than five years ago.

Johannes Mehserle testified Friday in federal court in San Francisco that he meant to use his Taser rather than his gun to subdue Oscar Grant on New Year's Day in 2009.

Mehserle is testifying in a civil rights lawsuit filed by Grant's father against Mehserle, the Bay Area Rapid Transit agency and other defendants.

Mehserle cried when he recalled seeing a bullet hole in Grant's back and realizing he had shot the suspect. Mehserle was convicted of involuntary manslaughter and served a year in prison.

Grant's father is seeking unspecified damages.