It sounds like he wanted to shoot them regardless of what was going on, and that does seem unecessary. Even so, I've not much sympathy for the thieves who got shot, as even though what the guy did
was over the top and probably unecessary, they put themselves in the position which brought about that act, so that's their tough luck. The simple fact is, if they had not been breaking and entering and stealing stuff in the first place, they'd not have been shot by him, and since they know that what they were doing was wrong, but they still did it, then they must have known that what happened to them was always a possibility.
I can understand frustration at reporting this kind of thing and the cops taking ages to turn up to a crime in progress, as I have had the same thing happen to me, where they took almost three hours to do something about it, but six minutes to respond is not actually that bad, the police can't be everywhere.
Chock