An officer was attempting to detain someone for drinking in the park at 26th Street and Treat Avenue at about 3:20 p.m., San Francisco police Officer Albie Esparza said.
The person started to fight the officer, and the officer opened fire, striking the suspect at least once in the lower part of the body, Esparza said.
The officer also suffered minor injuries during the altercation. Both the officer and suspect were transported to a local hospital to be treated for their injuries, Esparza said.
The suspect had been drinking with three other people in Garfield Square, Esparza said. No one else was detained.
The police officer will be placed on routine administrative leave while the incident is investigated, he said.
Anyone with information is requested to call San Francisco police (415) 553-1651.