Break up blues

My ex boyfriend and I dated for over a year. He told me he wasn't happy anymore and said he'd reached his limits over a phone call. I go to school with him and see him everywhere. I have never feared him, at least not until today. He was following me and a guy friend of mine around school until i finally left the school. He repeatedly called me and I ignored all of them. My friend took my phone and answered he called her a whore and a slut just out of anger. Im terrified of him now. His anger is taking over because I wont take him back. What do i do?!