Good luck with it. Maybe you will have to use a muzzle. Usually it is bad education, it can be inbred or both. But it is serious and years ago I had to put a dog to sleep because of it. I also had to do this with another dog with inbred behavioural problems. My aunt also had a boxer which bit people, I saw it myself. This dog lived al long life but it was a lousy and always potentially dangerous situation.