I am a heterosexual man.

In my class there are 2 guys I find weird. The first one is always trying to touch me (even when I am with a girl), he even stole my scarf to wear it. I avoid him and tell him to fuck off but it doesn't work.

The second one is always staring at me with a serial killer look. He looks away when I notice him.

How do I enforce boundaries ? Should I just stop caring about this ?