I'm truly sorry for your loss; but I feel I should suggest that PPRuNe isn't a suitable place for searching for information or reasoning behind a sudden death that happened nearly 2 years ago. If it was a surprise to you, it will, no doubt, have been a surprise to PPRuNers who knew him as well; and, I am sure, his family would prefer for such enquiries to be kept off the internet.
It does you credit that you continue to mourn him, and I hope you find the answers you're looking for.