Police have not identified the injured officer, who is in critical but stable condition at San Francisco General Hospital. Multiple news outlets report that the injured officer is Kevin Downs, a two-year member of the Police Department and co-founder of a nonprofit that aims to "assist in the reintegration of veterans," according to the organization's website.
Chaplin said earlier Saturday that the officer is partially paralyzed on one side of his body. He said the officer is assigned to Taraval Station.
Chaplin said information had been circulating that the officer's injury was a graze wound.
"It was a lot more than that," he said. "One centimeter down and this may have been a fatality for the officer. He underwent surgery to remove fragments from his brain."
San Francisco Mayor Ed Lee issued a statement Saturday saying, "Last night I received one of those calls that as a mayor you never want to receive. The phone call that tells you a police officer has been shot in the line of duty."
Lee said the officer was alert when he visited him at San Francisco General Hospital.
"He was able to communicate with me and I had a chance to thank him for his service," Lee said. "I have a good feeling that this officer will recover."
Chaplin said a town hall meeting will be held this week to give residents information about the shooting.
This post contains reporting from Bay City News and the Associated Press.