The drivers were on Bellaire near San Pablo when witnesses say an argument started.
The man was apparently on his way home from work when the incident occurred. He's a lawn maintenance worker.
Mark Johnson was a bystander during the incident and said he grabbed his girlfriend after hearing gunshots.
"I didn't know where to run, hide or what to do," Johnson said.
Family and friends said the victim has been unable to explain what transpired during the shooting. Deputies said it stemmed from road rage.
One of the victim's close friends said he is moving his fingers and responding. The friend added a message for drivers everywhere.
"If you have problems, don't get behind the wheel with a gun," the friend said.
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