Park police dispatch received two calls reporting a shooting near the San Francisco Fisherman's Wharf Hostel located at Fort Mason Building 240 just before 10 p.m., U.S. Park Police spokeswoman Chris Powell said.
Arriving officers found two people injured by gunfire.
A 22-year-old woman was injured by a bullet that grazed her head, Powell said, and a 17-year-old boy was shot in the stomach.
Both victims were taken to San Francisco General Hospital to be treated. As of 4 a.m., the injured boy was undergoing surgery and his condition was not known.
Witnesses reported that the shooter was a male who was accompanied by as many as eight other people, Powell said. He was seen wearing jeans and a black hoodie.
Park police have contacted the FBI and the National Park Service to assist with an investigation, Powell said. Areas within Fort Mason, which is part of the Golden Gate National Recreation Area along San Francisco's waterfront, have been shut down while the investigation is under way.