Well, I guessed wrong. The pilot had an H&K USP, not a Glock, which makes things even more complicated. The Glock is 'safe' unless the WHOLE trigger is pulled. It has a little tab on the trigger that deactivates 3 safeties at the same time.
The H&K USP, on the other hand, has three possible variants. Each starts out as a double action, and there's also a safety lever. This means someone was likely dinking around with the thing OR it was not 'de-cocked' after it's last firing and the safety put on. The gun had to be in "battery" to go off....and it did!

I too feel arms (guns, spray, knives, hiking poles, etc.) are as relevant to hiking/backpacking as anything else. It's all in where you hike and what the threat level is, as to 'if' and 'what with' you arm yourself.
paul, texas KD5IVP