In thinking about different scenarios and what I would do one that troubles me is this. You are in a store BG enters and shoots someone for effect then points gun at cashier and demands money. BG is not watching me and I am close enough to make a head shot if I was at the range ( not under stress ). If he did not have his gun pointed at cashier I would fire an aimed shot at his head and follow with multiple shots at torso. My concern is with his gun on cashier if I shoot him would he reflexively pull trigger and possibly shoot cashier? What is the physiology of this? Would a head shot make him go limp or would he tense and potentially pull trigger? What would you do?