Can you give him "time out's" in a shut room when he does that? Samantha was bad about attacking all mine when I finally got her and she wouldn't stop. I was at my wits end when I tried that and it only took her THREE days to figure out she did NOT like being shut in a room all alone and that bad behavior is what got her there. I think she is just so smart to figure all that out and realize she had to stop it or be shut up alone. They are still not the best of friends but she does not attack anybody anymore and that was last winter I think. Key here is you have to be consistant and do it EVERY time.... They HATE being shut in a room alone!