Six minutes before midnight, police responded to 17th and Mission streets and found three men who had been shot, San Francisco police Officer Samson Chan said.
One man sustained life-threatening injuries after he was shot in the chest. The two other men were each shot in the leg, and all three were transported to San Francisco General Hospital, Chan said.
The events apparently unfolded on the street, with the suspect and victims all believed to be on foot. The gunman was last spotted headed east on 17th Street, Chan said.
Police believe the incident was gang-related and the gang task force is investigating what sparked the gunfire.