I'm so sorry for their loss--it must be awful to deal with the death of a loved one so young (55 seems younger and younger to me these days!).

I think it's natural to wonder about the cause of death when it was unexpected or the person was young. In this case, though, it doesn't seem at all suspicious. Seriously, if they were going to make something up, don't you think they'd go with something more common? No one would question a heart attack in a 55 year old guy. The fact that the cause seems surprising makes me think that of course that's the real cause of death.

Sarah