Would breathing sound normal if you were somewhat in hypoxia and went into a bit of a trance?
I'm remembering a tube incident now - the 1975 Moorgate disaster - where they reckon the motorman (Leslie Newsom?) went into a trance of some sort and, keeping his hand firmly on the dead man's handle, drove the train straight through the station and hit the end of the tunnel. Wasn't drunk, or on anything, and was unlikely to be suicidal. I seem to remember he had hundreds of quid in his pocket to buy his daughter a car or something after work.
But then in that Egypt Air crash - the first officer who was blamed for murder-suiciding the plane was bringing care tyres home for his son on the flight! Not sure I'd bother if I was planning something like that.
Is there a piloty equivalent of the tunnel trance they reckon Mr. Newsom went into? If it was at night I reckon most would be saying he'd lost his spatial awareness.
Can I also add, as my SLF two bobs worth, that I'd rather pay a few quid extra and see three people on the flight decks again than, as others have suggested, further automation and removal of pilots. Three brains are used in most plane systems, aren't they?