How do I stop this

sa

This boy has been infatuated (obsessed) with me for at least 3 years now and I’ve blocked him and he made fake accounts to look at my photos on insta and he blocked me on Snapchat just to add me back multiple times. He’s not at my school anymore and I have multiple screenshots of our convos. He also claimed to commit suicide if I leave him. He even touched me multiple times without my permission and his sister would tell me “link with my brother and I’ll forgive you on everything” but I never did anything wrong to her. He even used the fake account he made on insta to dm my friend and ask her about her relationship with her bf. I try to ignore him but he really makes me nervous because the whole family’s mentally ill (my ex friend aka his sister told me and I had a feeling about it) so now I’m really scared because he’s been trying to get me for years now. (My friend told me he tried to force her to have sex with him in front of her ex which was his friend and he didn’t stop it)