It's a typical story that happens alot. They should be prepared. You have to look out for yourself and not care how they'll take it. If you're not, no one is.

(US Policy)
Usually, you have to give a written 2 week's notice and both of you need to sign it. Also, make sure you have a copy as well; never hurts, just incase. I have a feeling that your boss will take it pretty well. Just be honest with them when they ask why you left. If you stress that the reason is because you're closer to your home, they'll understand.