A lot of serial killers and such start off with hurting animals. To Ward's point it's important to figure out why your son likes taking apart animals... if it's because he likes seeing how different parts work, and wants to figure out how things work, a good behavioral specialist could work with him to rewire his reward centers to things like taking apart computers, clocks and other mechanical objects. You can essentially transfer the pleasure he gets to more benign activities. It's true for everyone, but from what I understand especially true of autistic children, it isn't enough to forbid certain activities, you have to transfer them to other activities.