It is simply not possible to rule this sort of tragedy out. . Suicide of a pilot, involving and often including all crew and passengers, is an unlikely but possible event. It will remain so. No medical examiner can identify this possibility with certainty. Nor can a sim examiner, line checker, nor colleague on the flight deck. Sad but true.There are quite a few pilot suicides (taboo words) which have occurred prior to report, and many in life between duties.