Break checking or doing anything aggressive when carrying is, indeed, a bad idea. That being said, the video certainly does appear to show the idiot in the Z-car pointing a weapon at the guy who fired through his windshield. When someone is already pointing a gun at you, shooting before that person is certainly justified. Was it the smart thing to do in this case? I don't think it was absolutely necessary. After all, he could have just slowed down and gotten behind the guy. It would have been impossible for the other driver to have shot at him in that case.