Autistic child with sudden aggressive behavior?

He could still be sick. Try putting him back on antibiotics. I doubt it's puberty at 9. Autistic kids go through these changes a lot. He may calm down on his own in time, or you can try medications. To be honest, most meds don't do much. Respirdal is prescribed by many, but the only thing it does for most kids is give them weight gain. Try Triliptal, Zoloft or Abilify or Geodon. Behavioral therapy is the best approach. If he gets really severe, you might consider bringing him to Kennedy Kreiger Institute in Baltimore. It's part of Johns Hopkins. They can combine med and behavioral and get very good results in many cases. My son was there for 6 months. Best of luck, it ain't easy, but hang in there.