Find out if he was entertaining a guest in the engineer’s cab when he approached the scene of the crash at 106 mph.
My guess - purely a guess - is a crazy suicide like the Germanwings pilot because of being rejected by his male lover(s) or catching him in an act of infidelity or some such. Then he threw on the brakes at the very end.
If this is in any way what happened then it’s too bad others died in his place.