If he is into that... part of the kink can be wearing the trophys afterwards. It isn't about nudity. It's about control and continuing to degrade them after death. That can involve wearing their clothing as a private little secret.

I'm not saying that's why. But if this isn't a troll, you keeping this from your parents and your parents ignoring it is what lets childhood kinks grow into a serious adult predator.

And he is one at this point. I honestly think you need to get him on some form of watch list, move out and far away, don't let your parents know your address and avoid him like the plague. Literally avoiding him like he was the bubonic plague.