I recently adopted an American Bulldog. He just turned two years old and had been neutered at six months. I read several sites and books mentioning that these dogs get along okay with other pets. He is such a loving dog when it comes to my girlfriend and I, my nephews and cats (loves cats!). However, I recently took him out to a dog park (yes, now I know.....never again) where he was apparently provoked by another dog.....before I knew it he had the other dog by the throat and was shaking it around. I obviously was completely taken aback. We got them seperated and neither dog was hurt. The dog he went after was the aggressor and being that I didn't see what happened, I figured the other dog threatened him (the owner also said he'd been bitten several times as he comes off aggressive). Anyway, again this weekend while walking my dog he went after another dog and again had it on it's back attacking at it's throat. This time I had told the person to keep his dog away from mine (the dog is my girlfriends brother-in-laws dog). I am completely shocked by this behavior and don't know what to expect. Is this somewhat normal? Or is there something else going on? Thanks for your help.