I'm sorry, but this is not a "training issue." This is inherited aggression. It was not allowed to develop -- it just came out of nowhere, and no amount of "obedience training" will turn most high drive dogs away from it's prey. Talk to owners on PT who have had dogs kill their cats, including myself -- and some who have had their own dogs kill their own cats. It was never an obedience issue. Telling a dog to "let go" of it's prey when it's adrenaline is pumping so fast it can not hear or think or see or smell or feel anything will not have any affect. I own high drive dogs, I have trained high drive dogs. I have dealt with working sharpness that will leave you bitten and bruised. Add aggression into the mix and you have a recipe for disaster that no amount of training will control entirely. This does not mean the dog should die. It just means it should not be allowed into certain situations. Hence why Baby is now wearing a muzzle 24/7. You can not always train out a behaviour but there are other ways to avoid dangerous behaviours without unnessecarily putting the dog to sleep. Just as I have friends who avoid having their dogs with cats, with men, with children, etc etc etc.