A man was arrested Tuesday on suspicion of shoving another man into an oncoming train in San Diego on New Year’s Day, killing him in an unprovoked attack, police said.

Ryan Michael Rukstelis, 26, is suspected of pushing Martin Andara, 68, off the platform at the Old Town trolley station on Saturday morning after they both got off a trolley, police said.

Andara hit the side of a moving train and died at the scene.

Rukstelis was booked on suspicion of murder and held without bail. Police said he doesn’t have a permanent address.

It wasn’t immediately clear whether he had an attorney to represent him.

Police haven’t released a possible motive for the attack.