Call him everyday. Seriously. My dad had the same thoughts about his friend and he hung himself in the end..
My dad said he wished he called everyday..
So seriously, call him, text him, go see him and don't leave until you talk.
(Even if its not related to his absense, that may make things worse)
You may feel like its a lot for you to do
But dude
Your his FRIEND.
You'll thank yourself in a few years for helping him and he will appreciate it.
Sorry, death is just to much of a serious matter to even be considered light.