We have places for people that do that.
Prison.
So, you have a stranger in your house at 2AM; someone not known to your family (you have asked!) That stranger is within the most dangerous age bracket. This stranger is in close proximity to your daughter and to you. At this point you call 911 and continue watching the intruder, in case he attempts to hurt you or others.
It was when the boy made a sudden move, as if to grab something, the 55-year-old man opened fire
If that "sudden move" theory can be confirmed, the father should walk. The intruder, even unarmed, could take the daughter hostage and threaten to break her neck with his bare hands. It's certainly possible, since the daughter denied knowing the boy.
You'd get the same treatment from a police officer if instead of staying in your car you jump out and rush toward the officer - to show him your license and registration, of course. There are situations when one must behave exactly as told, due to man-made or natural dangers.