My boyfriend has a pitbull who grew up around cats for years. He lost his dog when he was 6 & recently got him back so now he is 9. He killed my friends cat even when I was telling him no & hitting his nose to get him to let go. He wasn't growling or making any noises. My boyfriend & I are moving in together soon & I have a cat. I brought her over to introduce them & all he wants to do is attack her. He whines & shakes & goes crazy when he gets a little close. He's not aggressive towards humans at all, but he doesn't listen once he finds his prey. We put her in a small crate so he won't be able to attack her, but he barks & growls & does whatever he can to attack her. Please help!! I dont know why he does this. I'm scared even if they get comfortable that he'll attack her out of no where. Because of my experience with my friends cat.