Most Helpful Guy
just tell him as nicely and politely you can. there is no way he's not going to get hurt if he likes you so that's it basically.
Most Helpful Girl
It's inevitable that you will hurt his feelings. These things are always painful no matter how nicely we try to put them. Be honest with him, tell him what you wrote on here, don't make up any excuses and don't promise him things that you know aren't going to happen.