Most of the times pitbull aggression is not normal. Your dog may also have the behavior problems and it may feel insecure. First get him to a vet and get the suggestions to change or modify the behavior of the puppy. Also get the obedience classes for your puppy, it will surely learn there. Moreover, also tape its mouth off when he shows off such a behavior. k9deb.com
I suggest you watch television and look for a program called "The Dog Whisperer". It is usually on around 11pm, as this man clearly knows how to treat an animal civilly. GOD BLESS & GOOD LUCK TO BOTH YOU AND YOUR PUPPY.♥