I have this pit/bulldog mix that I frequently sit, but this is the first time I've noticed a slight change in his behavior. This time around he's randomly becoming aggressive when my roommate comes home, or when he sees my cats he will give chase and looks ready to kill them. He's never paid any mind to my roommate before, or my cats, but now he growls and barks loudly at random. One day my roommate comes home--no reaction. Then later in the day, he will go ballistic. I've raised dozens of litters of dogs and trained them, but I've never quite had an issue like this. I dont know what could be triggering him, but its getting to the point where I'm afraid to leave, or even sleep, without the dog locked in a kennel for fear he will hurt my roommate or my cats.

He is very sweet with me, but that seems to be about it. He is a free roaming dog, so being in a kennel is very stressful for him and I don't want to make his stay uncomfortable. I haven't told the owners yet, because they've never told me anything about their dog being aggressive--and I've never seen anything until now--so I'm trying to think of things that might be setting the dog off. Any ideas? I'm in a quiet neighborhood, he gets 4 40min walks, but usually he loves to just lie on the couch with me. He gets fed adequately, and lots of belly rubs. The cats will just be sitting on the bookshelf and he just whines and barks and jumps for them.