[cos]

It sounds like he's a pretty bad resource guarder, which is really tough when it's with other dogs and not humans because it's hard to train out of them and most people recommend you let the dogs work it out - however in the situation where there are pets being killed that's not really a good option.

Stop getting cats, is one piece of advice I'll give you - or other dogs. It sounds like this dog can't be trusted around cats and other dogs, so while he's in your hands I wouldn't get any other pets if I were you. Some dogs need to be the only dog and that's okay. It's better to enjoy one animal than to be continuously heartbroken over the death of many others.

When you feed him, make sure it's separate from any other animals - even small treats. Don't feed him near the other dog living there.

I agree with Tracie, I would definitely speak to a good positive reinforcement trainer and see what they can do and how they can help you work through this for the best interest of the baby. It could also be entirely possible that this dog can't be trusted with a baby, but I'm sure the trainer can help you determine this.

 

[cos]

My opinion would not be a popular one, but generally is enforced by the law. One dead animal, seek professional help. Two dead animals, euthanize. Since that would be unpopular, still seek professional help and absolutely do not allow your dog to be around kittens or other small animals. I would even be hesitant allowing your dog around other animals and children period.

In this case I think that since the fault was the negligence of the owner bringing in another animal after one had already been killed, professional help should still be sought out since that option hasn't yet been exhausted. Euthanizing a perfectly healthy animal before training attempts is cruel and unfair, and suggesting that at this stage - in my opinion - is extremely irresponsible.

 

[cos]

@cos - Hence why I stated it merely as an opinion and not as a suggestion? The actual suggestion being to find a professional for help.

It could still look like an easy way out for someone and as an opinion could come off as a suggestion.