Police say 30-year-old Stephen Martin was assaulted around 5 p.m. on May 20, 2012, in the Sharon Meadow area of Golden Gate Park, hours after the 12K race had ended.
The Santa Clara resident and his friends were wearing troll costumes and got into an argument with another group, apparently involving a dispute over a cellphone. Someone in the other group then punched Martin, who fell and hit his head on the ground and lost consciousness.
He was taken to San Francisco General Hospital where he died on June 8.
"It was basically a sucker punch," police spokesman Officer Albie Esparza said.
Esparza says investigators are continuing to review photos of the group that was arguing with Martin's friends and are again asking for the public's help in identifying the possible suspects.
In the photos released by police, the males in that group were wearing red and white 49ers jerseys while some females were wearing purple clothing and one wore an orange tutu, police said.
Anyone with information is encouraged to call the Police Department's homicide detail at (415) 553-1145, the anonymous tip line at (415) 575-4444 or to send a tip by text message to TIP411 with "SFPD" in the message.
