Is this a Bullie or just a Jerk?

Their are these kids at school who are just suddenly picking on me. At school I am kind of shy, but in real life I am actually pretty cool... But just recently whenever I go to my locker after lunch this group of kids just stair at me, not like regular, i mean eyes wide open, and most recently they said where my locker is, is their turf! Plainly I think they are just jerks! But what do you think, and what should i do about this problem?