Huan Chen, 83, was attacked by a group of boys on Jan. 24, 2010 -- three years ago Thursday -- after he left a San Francisco Municipal Railway light-rail stop at Third Street and Oakdale Avenue and was walking to his assisted living facility, police said.
Chen was struck on the back of the head, causing him to fall to the ground and hit his head on the pavement. He was taken to a hospital where he died two months later, according to police.
The teens fled and have not been found.
The mayor's office has authorized a $100,000 reward for any information leading to the arrest and conviction of the suspects in Chen's killing.
Anyone with information should call Inspectors Kevin Jones or Pamela Hofsass with the Police Department's homicide detail at (415) 553-1145, the anonymous tip line at (415) 575-4444 or should send a tip by text message to TIP411 with "SFPD" in the message.