You do your son a disservice in making him seem like this "almost" tough guy. Servicemen are trained, briefed on the situation and are given guns ahead of time so that they are prepared "to get busy" in the situation at hand. That's not the same as being caught off guard with gunshots towards ones face, with loved ones to protect - that changes the dynamic completely. The natural instinct is to protect - not attack.
Having served in the Navy I can tell you with experience that the two times I found I had my gun drawn on another man in civilian life I found myself praying to God that I don't have to shoot another man and I'm very thankful I didn't. There's no tough guy in a real situation of this nature.