The gunfire in the 4100 block of Hilltop Drive was reported shortly before 10:30 a.m., according to San Diego police.
Medics took the victim to UCSD Medical Center for treatment of a gunshot wound to the chest. His condition was not immediately available.
The assailant was described as a roughly 5-toot-9-inch black man in his 20s with a short afro. He was wearing black shorts and a white tank top, SDPD Detective Gary Hassen said.
The motive for the shooting was unknown.