The incident began shortly before 11:30 a.m. near Garfield Avenue, when the CHP and Los Angeles County Fire Department responded to a report of a pedestrian described as a psychiatric patient walking on the freeway.
According to a CHP report, officers initially received a call about a crash involving the man.
When they got out to check on him, shots were fired, though details about the shooting were not immediately available.
The man was transported to St. Francis Medical Center where he later died.
No Highway Patrol officers were injured in the confrontation.
Video from AIR7 HD showed westbound traffic backed up for miles as investigators combed the location for evidence.
No estimate was given for how long the lanes would remain shut down.