I honestly can’t tell what is going on at the critical and following moments in that/those videos.
But I believe that the body cam clearly shows that the officer was not dragged by the car. Regardless of what the three police officers say. If he wasn't being dragged then were is the threat that justified using deadly force?
I watched it several times and what I saw was this:
Dubose becomes uncooperative and the cop moves to open the door. Dubose puts his hand on the door to keep it from being opened and moves to start the car, or shift it to drive. Cop tries to grab Dubose’s far hand to stop him and also has a gun pointed at Dubose. Based on the cops angle at the time of the shot the car couldn’t have moved more than a couple of inches, if at all, when Dubose was shot.
I think what is most likely is that the cop drew his pistol when Dubose became argumentative, practiced poor trigger control, and fired when surprised by the movement of the car. Still a crime but with mitigating circumstances.