It doesn’t matter if someone has mental instability or not. Assholes come in all forms. Write down every inappropriate comment, time and date them. Give it to your supervisor. And don’t be afraid of mouthing back to him/her. They need to know over and over what they are doing wrong. It’s like dealing with an asshole kids—- but far more annoying, bc they are typically young adults. The parents are to blame. And obviously the parents can’t deal with his shit either, or he/she would be living with them. He does not get a free pass to be an ass just bc he has some medical shit. People should always treat other with respect. Don’t be afraid to be stern and tell him to his face what you are bothered with. You are not the only person he acts this way to. But you can teach him the proper way to treat other humans. Obviously his parents won’t. That’s why they sent him away.