Yes, get him into some counseling and also keep the dog in a supervised place when he is with your son.
I would consider counseling. What is going on in your child's life? This type of behavior is often, though not always tied with a child feeling frustrated or angry at himself or others. Is he bullied? How well does he get along with teachers? Babysitter etc.
I agree with penswriter. Animal abuse is often a prelude to more serious abuse. In any case I would not keep the dog.
Your child should be supervised at all times around this dog, if he continues get a home for the animal. .
that is most certainly NOT normal. I would HIGHLY advice rehoming the puppy immediately!! Other wise next time, the pup may end up dead. And get your son into some sort of therapy ASAP.