Speak to Rabbi Wallerstein. He will be very helpful in such a situation. At the very least he can guide you what is the best way to deal with him.
Obviously this child is very hurt. Something happened to him that has caused him so much pain that he wants to rid himself of yiddishkeit. It could be something that happened between him and his parent, or something that happened that his parent either didn’t support him with, or it could be an issue in the home where this parent doesn’t respect the other and that has turned him off. There is a long list of what it could be, but without a doubt this child is hurting badly and Rabbi Wallerstein has much experience in dealing with children in pain.