I'm mad at my friend for not paying up
Why do you think he's not paying you back?
He is probably angry at me.
Even if they are angry at you they should still pay their debts. You shouldn't be friends with someone like that.
He does owe me though. I don't care how he feels, guess I just have to go to the cops.
Do not call the cops on him. Give your friend time to pay you back. Even though he is angry at you, I believe that he will still do it.