The shooting, in which the victim was struck several times in the upper torso, occurred about 5:30 p.m. in the 14400 block of Dinard Avenue in Norwalk, according to the Los Angeles County Sheriff's Department.
The man was pronounced dead at the scene. His name was not immediately released.
It was unclear what may have led to the shooting.
No description of the suspect was available.
Anyone with information about the incident is asked to call the sheriff's Homicide Bureau at (323) 890-5500.