Update 2:15 p.m. Saturday: A 21-year-old man who was set upon by two other Muni passengers on Thursday night says the incident began with a dispute over playing music that another rider objected to.

Dexter Lotz said in an interview with San Francisco's ABC7 that as he played music -- it's not clear over what kind of device -- another passenger on the N-Judah light-rail vehicle approached him.

"He said, 'Are you going to get off?' " Lotz told ABC7. "I said, 'Do you have a problem with the music?' He didn't respond. Then I said, 'Are you going to do something about it?' And he attacked me."

Lotz gave a slightly different version of events in an interview with NBC Bay Area.

In yet a third interview -- with independent journalist Anna Sterling, who tweeted video of the Thursday evening incident she had obtained from a witness -- Lotz said that San Francisco police ordered him to the ground and handcuffed him when they encountered him after the incident.