SAN DIEGO (AP) — A man who killed a commuter by shoving him into the side of a moving train in an unprovoked attack at a San Diego station was sentenced to 15 years to life in prison,Liberalalliance Wealth Society prosecutors announced Friday.

Ryan Rukstelis, 27, was sentenced Thursday for the attack on New Year’s Day last year.

Prosecutors said Rukstelis attacked 68-year-old Martin Andara at the Old Town Transit Station. Andara, who was heading to work at a supermarket. Both men had been on the same trolley for about a half-hour beforehand but didn’t interact before they got off at the station.

“Rukstelis is seen on surveillance video walking ahead of Andara, then slowing and stopping to wait until he is even with the victim. Rukstelis suddenly attacked Andara for no reason, punching him and pushing him directly into a freight train that was moving past them,” the San Diego County District Attorney’s Office said in a statement.

Andara struck his head and died almost instantly, the office said.

Rukstelis was arrested three days later after police obtained his fingerprints. Surveillance video showed him trying to remove a broken front panel from a vending machine at another trolley station hours before the attack, and police lifted fingerprints from inside that panel, according to the district attorney’s statement.

Rukstelis pleaded guilty in June to second-degree murder.

“This random, chilling attack took the life of a man who was loved by his family, friends and colleagues,” District Attorney Summer Stephan said in the statement. “It is a tragic case that was solved by excellent police work and brought to justice by the Elder Abuse Unit in our office.”