I'm shattered. I am pretty sure my grandson is now in porn films. What should I say?

This kid had a terrible childhood with hunger and cold nights when he wasn’t staying with us. His mother is bipolar and has taken drugs since she was fifteen. He sold drugs until he moved near us and began junior college and is on the Dean’s List. He craves income; he buys and sells cryptocurrency and has student loans for nursing school. But lately he has been driving to Dallas with his roommate for the weekend telling me they’re “making films and he’s playing the doctor” but he wont tell me anything else. We had the nicest birthday dinner lately with gifts and his first legal drink. Then late that night he was off to Dallas with his roommate, I asked questions and he won’t answer me now. I have a full range of emotions none of them positive. What should I say? I don’t want him over here for a month “to save $400 for the dorms” but I told him “sure” when he asked before I knew about these movies. He looks so innocent, sweet and smart. I“m shocked and grossed out.