I can understand that sentiment about your mate. When I was only 28, my next door neighbor, who was also 28 died of a heart attack. Turns out it was genetic and ran in her family, but it was very hard to fathom at that time, someone my own age perishing. Heart attacks were certainly something I wasn't worried about at that time, those things only happened to old people ! Even I was amazed at how very much that affected me at the time.
When people say "you just never know"... it is true, you just never know !