My condolences to the wife and family.
There is a project going on to determine whether or not this sort of thing has a genetic cause.
If his father or any uncles died suddenly at a similar age it might be worthwhile to get any or all of his children in the project. If they have the suspect gene, there are therapies available right now that might prevent a similar situation in their lives.
I can provide a contact to one of the leaders of the project.
Again, my condolences to all.