child doing scary acts

My grandson, age 9, is throwing the cat up in the air, holding cat very tightly so cat cant get away. He has hit his baby sister in the stomach when she was about 3 months old. He was about 4. When he is out of control, if I put my arms around him to tell him goodby, he tenses up, I can feel him pulling away. once he was sent to his room, and he tore the bedding off, He screamed, He laughs at you. He is always in trouble in school, talks back to the teacher. He wets the bed. He is on medication now. He seems like he has no compassion for anyone. But if he gets hurt he is very upset. Most of the time he dosent answer when he is spoken to. I am afraid of what he might do. What kind of medical help should my son and his wife seek?

[Kevin Kennedy, Ph.D.]

Depending on what his parents have already done (since your grandson is on medication, some intervention occurred), they should seek an evaluation by a pediatric mental health clinician. The symptoms you describe can typify several emotional disorders, so an accurate diagnosis and plan for treatment (including ongoing therapy, collaboration with school, and parent guidance, in addition to medication) can be effected.