Step son said it was sweat but I'm pretty sure it's pee

Me and my husband have been having issues with his 17 year old. He's been staying in trouble and has even gotten in trouble with the law. We think he's acting out because he recently got out of a bad situation when he was living with his mom and step dad. He has some really bad PTSD from some horrible trauma. Thats why I'm trying to be patient with him. But he is constantly disrespectful. Hopefully therapy will help. So the person who does the laundry rotates every week. This week it was my daughter's turn. She's 14 and my step son is on dishes. We were all in the living room and my daughter runs in with the laundry basket and yelled that Jason had peed on his bedding and showed us. My step son said he didn't pee and it was sweat an he got really mad. She was saying "No it's pee!" He was now yelling that it was sweat and took the laundry basket and threw it. His face was red and he slammed his door. I helped my daughter pick up the laundry and when I found his bedding it did look like he peed. Usually when I sweat it's in multiple areas of the bed. There was just one giant wet spot and it smelled like urine. If he is peeing the bed then I think someone should talk to him about it but with that reaction I don't know if it's a good idea.