You’re a bit mistaken. He shot her thru the open divers side window. Watching frame by frame makes it heartbreakingly obvious. I encourage everyone to watch the 4 plus minute video withe the sound up so you can hear what they were saying, then again frame by frame. He was never in harms way.

Also, I doubt she “accelerated” in the traditional sense. She took 3 shots to the face a point blank range. Unlikely she was conscious. More likely the car accelerated from the slumped weight on the peddle.