He probably should not have shot them AT ALL, unless he could see that they were armed with firearms. Even if they had had a bat, or a knife, I think I would have told them “FREEZE!” while aiming at them.
google ‘Tueller Drill’.
If someone breaks into your darkened house in the middle of the night and you take time to see if they are armed you will die. I always assume that they are intending to kill me. I will shoot them dead.