Investigators said that the shooter was in another car, the Los Angeles Times reported.
The shooting occurred shortly before 3:30 a.m. on the southbound 101 Freeway. Police and the California Highway Patrol received calls from witnesses first of shots fired and then of a car being driven erratically.
When officers arrived at the scene, they found the victim slumped over the steering wheel. Another driver trying to assist him had broken the window to get into the car.
Police had not released the victim's identity but said his last address was in East Los Angeles.
"His prognosis is not good," said LAPD Lt. Paul Vernon.
The car still had temporary license plates, which read "Dream."
Investigators were trying to determine the type of gun used in the shooting from the bullet holes in the Bentley.