I have an 11 yr old black shepherd, Raven, who has been raised with cats. Recently he has been going after the cats and has subsequently killed 2 of them. I have 2 other dogs, also. There is one cat left, Snowball, who is Raven's buddy but I have caught him charging after Snowball. I am keeping the cat in a separate room when we leave. This is not like Raven something is wrong. Please help, this was horrible what happened to the cats?