The thing is she didn’t floor it. Didnt even pull away quickly. He could have stepped out of the way… he in fact did, right after he pulled the trigger and shot her. He literally stood in front of the car, pulled his gun and basically said “move the car and you die”. He put himself in harms way, pulled his gun and escalated the situation.
This will in all likelihood be deemed a justified shooting by the police and court, but with a little compassion from the officer it could have ended without this lady being dead. Bet he doesn’t even care.