My son smashed our living room tv

I really thought my son opening up would be the start of us building back the relationship we once had. My son is in therapy because the last 2 years he changed on me and just started getting into trouble with stealing and lighting stuff on fire becoming very disrespectful. His therapist diagnosed him with PTSD but wouldn't tell me what from. Therapy has helped him and he's sorta stayed out of trouble but still acts out sometimes and gets disrespectful. In therapy I was asked to stay and he opened up to me about his friend (I'll call him John) who he was experimenting with 2 years ago (My son would have been 14 and John 16) and he decided he didn't like oral and didnt want to finish john off. John got mad because he finished him off and put him against the fall and forced himself onto my son without his consent. He didn't look at me. I hugged him and cried but he pushed me away. The past week ive been trying to get him to talk about it. He wouldn't so I will admit I kept pushing and wanted to talk about it and when he wouldn't talk about it I said "Fine. If you won't say anything I'll just go to the police and report it". My son went ballistic yelling at me and said he regrets telling me and knocked our flat screen TV on the ground shattering it and left. He ended up at one if his friends house because the mom called me. He has been over there a bit to calm down. I know I upset him by pushing this, but I just figured him telling me was us finally communicating.