What is the legality of this situation?

This guy in my Dad's neighborhood was burglarized about a week ago. The guy said that he saw someone run through the hallway when he was in bed, so he went and got his shotgun. He went downstairs and saw a figure rummaging through the cabinets so he turned the tactical flashlight on. When he got a good look at the man, the guy started towards him so he shot him. It didn't kill him, which surprises me since it was 00 buckshot from like 5 yards, but how much trouble is that guy in and was it justified?