The CHP officer was driving a patrol cruiser about 9 a.m. when he "came under fire" at the intersection of Third Street and Ford Boulevard, sheriff's Lt. Patricia Thomas said at a news conference.
LASD deputies who were in the area were also shot at by the gunman, and they along with the Highway Patrol officer returned fire, Thomas said.
One of suspects, identified only as two men, was shot in the exchange and transported to a hospital, authorities said. The second suspect fled the location and remained at large.
The condition of the hospitalized suspect was unknown. No law enforcement personnel were injured.
A handgun was recovered at the scene, Thomas said. Video from AIR7 HD showed the rear window of a Highway Patrol car was completely shattered.
Bystander video captured the moment a barrage of bullets were fired during the shooting.
Investigators were looking to examine surveillance video for possible footage of the shootout, the Sheriff's Department said.
The suspect's motive in the shooting was under investigation.
A description of the suspect being sought was not immediately available.
Anyone with information about the incident was urged to call the Sheriff's Homicide Bureau at (323) 890-5500, or Crime Stoppers at 800-222-TIPS.