I would echo Callmebj. Just be yourself, and make sure he knows that you're there for him when/if he needs you to be.

You have to take a little solace in the rather hard fact that while there's nothing you can say that'll make it not hurt, but plenty you can say to ease him though this. The best you can do for him is to be there for him, and make sure he knows that if he needs you, you're there. That's really all you can do.

I will keep you both in my prayers.