Many things about this depend on what jurisdiction your in and what your Attorney General feels should be prosecuted. If your state allows Castle Law to extend to your vehicle then this is a legal no-brainer as you are allowed to defend yourself as soon as he tries to breech your car with his handheld weapon. You can either use your firearm or run him over or crush him in between vehicles if you do not want the 2-mile liability of a stray round. Just be sure not to try something like "knocking him down to immobilize him" with a vehicle; a reasonable person, a judge and any Attorney General would qualify a 4,500 lb vehicle as a "Deadly Weapon" at any speed. Just remember, type of weapon does not matter in the eyes of the law - if you are justified in killing him, you can shoot him, stab him, run him over, throw him off a building, hypnotize him to walk into a fan, whatever.
If your state law or your personal convictions does not allow you to take his life unless he is putting holes in you first, make sure to use the surrounding area to your full advantage. For example, when someone is trying to kill you, drive on the sidewalk! Also honk to try to get drivers in front of you to move. If they don't, put your car in first gear and move them - that's what bumpers were made for. Push between two cars, especially if one is partially turned, it will spin away when struck and you will free yourself. Do not stop for red lights, stop signs or anything else. The fact is you are TRYING to attract the attention of the cops or get someone to call them! The worse your behavior, the more likely that someone will call the police and you will get help! Again, this is to evade the attacker at all costs and leave him alive; it seemed like the guy in the video was more worried about getting a ticket for running a red light or going on the sidewalk than getting his family to safety, but as always, the video might not have shown everything.