Trying to find the right words

One of my friends lost his son to suicide 2 days ago. I know I need to call him but I'm having the hardest time finding the nerve and the right words to say. It makes no sense that I'm nervous about calling a friend who I always talk to so easily. What should I say? Does he really want me to call? Is he tired of talking about it? I can't even begin to understand what he's feeling. So sad to think about. His son was the same age as Adam.