Dave, it's difficult for people to admit their mates could have screwed up under these circumstances; I understand that and I'm no different. We all do it, and fortunately for most of us it hasn't been a situation that hasn't been recoverable.
It is not, however, insensitive nor disrespectful for those who post here to speculate on possible causes and that's what I see. To suggest that it is, is just emotion talking, and I also understand the depth of that.
There is nothing illegal, immoral, indecent, nor against forum rules to speculate on possible causes, even though nobody knows with any degree of certainty. 3 holer, you are abolutely correct about that.
However, there are two possible causes
Failure and loss of control
Catastrophic failure
As I see it, the only other possible is crew incapacitation, but I'd put that at about .001% or less, but not an impossible chance.
Jabawocky, you were in a difficult and unenviable position, but if you've gone some way to consoling an elderly mother, then well handled.