Two women and a man were injured in the shooting on the 1100 block of Palou Avenue, which occurred around 1:30 p.m., police spokesman Officer Gordon Shyy said.
Witnesses reported seeing the victims drive themselves to the hospital, and a short time later, two women and a man arrived at San Francisco General Hospital with gunshot wounds, Shyy said.
Shyy said he did not know the extent of their injuries or the victim's ages.
While early reports suggested as many as three male suspects were seen fleeing the area, Shyy said it now appears one male was seen running on foot down Harbor. He then got into a white vehicle and drove away.
The first suspect was described as a black male wearing a green hooded sweatshirt and light blue jeans, while the driver was described as a black male wearing a white tank top undershirt.
Both suspects and the vehicle remained at large as of shortly before 4 p.m.