Most Helpful Guy
just walk up to him and look him in the eyes and say "we are done"and simply walk away
Most Helpful Girl
If you're scared to talk to him face to face, why not write him a letter go right up to him, hand it to him, and tell him to read it right then and there. Then you're not talking, but it's still faced to face. I'm sure he'll have some input after reading it, but you might feel more equipped, and have more time to think.