how to tell a guy to back off?

there’s this guy that has constantly been following me (he goes to my church so it’s not at school, but every single time i’m at church/ a church event) wherever i go, gives me no personal space and we are not close nor are we friends at all. he’s quite taller than me and towers over me but also sometimes gives me this death stare from afar. i never feel alone anymore and it’s kind of making me fear going to church. it’s not like i can just push him away or scream at him to leave me alone because were in a peaceful christian environment... i just don’t feel as safe anymore. please tell me i’m not the only one that thinks this way??? :(