If an officer was pointing a gun at me, I hope I'd have the sense put my hands up where he could see them. I'd not try to drive off.
Having said that, I've been held up at gunpoint in real life in South Africa (not by a police officer) and my first reaction was to run. I didn't calmly consider my options. fear & instinct took over instantly.
Was the officer following their training? If police protocol says an officer should open fire if someone refuses to stop immediately, then that protocol needs changing. If an officer can't shoot out a tyre from 6 feet then they really shouldn't be carrying a gun.
It's horrifying but in a society that insists on the right to carry a gun, mistakes happen. Officers have to assume everyone is armed. I would want to know more. Did the owner of the car have a history of gun crime? What else had happened?
Honestly, you couldn't pay me enough to live in the US or SA, and I'm white.