My son got touched inappropriately at a sleepover

I hate to make a post like this after having such a positive update. My 17 year old son is transgender and his friends found out when he period randomly came back while he wad sleeping over. The mom was very sweet and sympathetic. And the son of the mom came over and gave him some chocolate and played Xbox with him. Didn't even mention the period accident. The rest of his friends did have questions from what my son said but everything seemed to be okay. He went back over that friends house Friday and he came back home at 6 in the morning crying. When I asked what happened he said he woke up to one of his friends hands down his boxers fingering him. He pushed him off and ran out the door and left his bag and stuff. The friend that came to see him according to my son has NOTHING to do with it and was asleep. That friend was even texting him asking where he was and why he left and the mom messaged me too asking if he was okay and he left his stuff here. My son said to me not to tell anyone and he shut off his phone because he doesn't want to talk to anyone. His friend cams by to drop off his bag but my son said he didn't want to talk to anyone and he wanted to be left alone. He obviously does not want to report this or talk about it but this is so disgusting. The boy who did it is 18 and can and should be charged as an adult!