If you're comfortable doing so, just let him know that you're there, and you're thinking of him, and that if he needs/wants to talk, you're available. Any time I've been grieving a loss, I just needed to know that folks were there if I felt the need to talk or have a hug or whatever. I usually restricted that to the folks closest to me, but knowing that others were thinking of me reminded me of all I had left. A connection to the world of the living while faced with death.

Best of luck and hugs on general principle.