How?
You can't always stay around a dangerous area after a shooting, sometimes you may need to leave because the scene is still hostile or dangerous, for multiple reasons. Possibly more attackers, maybe gang members are involved(sitting around waiting for more bad guys to show up is not a good idea)
Put yourself in his shoes, if two men walk up to your vehicle, start beating on you and try to rob you, fight or flight kicks in. How easy is it to retreat?
How easy is it to pull your weapon and fight?
Every situation will differ from person to person, I'd like to see more info on this case if possible.