planned to get in his car, cause a road rage incident, and somehow force the physical altercation wherein he was planning on causing death, it cannot be premeditation.
But it also isn't self defense since the guy easily could have kept on driving, not followed the other guy into a parking lot, and not gotten out of his car. He chose to get in a fight (illegal) and a man died due to his actions. He has broken the law and is guilty of manslaughter, though he might be allowed to plea to a lesser crime.