CONTRA COSTA CO., Calif. -- A 49-year-old former BART train operator was charged last week for allegedly inviting a woman into the front cab of a train and then making sexual advances toward her, a spokeswoman with the Contra Costa County District Attorney's Office said Thursday.

Calvin Tom was charged Oct. 28 with misdemeanor counts of soliciting a lewd act in public and false imprisonment after the incident, which occurred on Aug. 4, according to Patricia Daniels, spokeswoman for the district attorney's office.

A warrant has been issued for Tom's arrest, Daniels said.

Tom resigned from his position before BART completed disciplinary proceedings against him, BART spokesman Linton Johnson said.

The incident began when Tom invited a woman and a child into the front cab of the train he was operating, according to Johnson.

The woman alleged that he made sexual advances toward her and then blocked her from leaving the cab, Johnson said.

The woman eventually escaped and reported the incident to authorities. Tom resigned shortly afterward as BART was starting the disciplinary process, according to Johnson.