dearie
there are people and there are animals.
We call murderers animals as a figure of speech which reflects rather harshly on the animal at times.
We don't kill people because they are generally considered to be different to animals.
Whereas dogs that kill, what are you going to do with them? Retrain them to be nice obedient dogs? Put them in a psychiatric ward for dogs?
I find your question very bizarre and ill educated.
I can only assume you are a troll out to rake up a bit of controversy.