At about 2:30 a.m., the city's ShotSpotter gunshot detection system was activated in the area of McKinnon Avenue and Newhall Street, Sgt. Michael Andraychak said.
Officers responded to that intersection but didn't find any victims, he said.
However, a short time later, a wounded 34-year-old San Francisco man showed up at San Francisco General Hospital, Andraychak said. He had been shot but his injuries were not life-threatening.
Investigators have since gathered that the shooting stemmed from an argument near McKinnon Avenue and Newhall Street.
The shooter is described as a black man between 40 and 45 years old, Andraychak said.
He said the shooting is not believed to be gang-related.
Anyone with information on the case is asked to call the Police Department's anonymous tip line at (415) 575-4444 or text a tip to TIP411 (847411) and reference "SFPD" in the message.