You could be right, maybe I misread the story. I read it that the men were out of their cars when the BMW bureaucrat got back in and rammed the Prius. But you could be right and Prius guy was in the car when he was T-boned in which case clear self defense. Ramming a car intentionally with a person inside it is assault with a deadly weapon.
My read is that when the two pulled over, Mr. BMW confronted Mr. Prius and Mr. Prius went back into his car until LEO arrived. Then Mr. BMW got in his car, T-boned the Prius on the driver’s side, pushed it through the lot, and shot at Mr. Prius. Then Mr. Prius shot back at Mr. BMW, striking and mortally wounding Mr. BMW through the BMW’s windshield.