Turning on the owner is a VERY scary experience, especially once it starts breaking skin. Our late boxer, Dempsey, became EXTREMELY door aggressive at home. If anyone rang the doorbell or knocked on the door (or if he heard a doorbell on tv - remember that annoying ad where the doorbell rang all the way through the ad?), he'd charge the door in full code red alert. Nothing, and I mean nothing, would deter him. He actually chewed the door knob into an unusable hunk of chewed up metal. After turning on me multiple times when I tried to get him away from the door, we regretfully returned him to the rescue we got him from, and his former foster family took him in to see if he could be rehabilitated (I told them all I'd already tried). He was assessed by 2 well-known trainers/behaviorists (plus his foster dad was a military dog trainer), but it was finally recommended that he be put down. RIP Dempsey. It was very sad for all of us, including his foster family.
This was the same dog who was a perfect angel in public and out on walks. At Petsmart, 2 year olds were perfectly safe climbing all over him. Also, once a person was inside our house, he was perfectly fine and sane. The doorbell/knocking was the trigger that sent him over the edge - literally. When our grown children visited, we'd have them call right before they arrived and crate him until they were inside the house (they were asked not to ring the doorbell or knock), then he was perfectly fine when we let him out.
We tried all the known desensitization therapies with him, with no luck. Sometimes, the best training still doesn't work. We think that Dempsey had something in his past (he was a rescue) that caused him to become mentally unstable, and that once he started feeling that we were "his people", that it triggered red zone response to people entering our house.
OP, I hope you get professional help for your dog. Only a professional can properly assess the level of instability and apply the proper techniques needed to change the behavior. Just know that sadly, even the best therapy sometimes isn't enough. Best of luck to you!
