The guy was experiencing a severe panic brought on by his mental condition. His disease caused him to step over the line when he said the word "bomb". Everybody who flies knows that from the time you park your car in airport parking until you get to your motel room at your destination, "bomb" ceases to be part of your vocabulary.

This may be the first case of air marshalls shooting someone who exhibited threatening behavior brought on by mental illness, but it's certainly not the first case of authorities, in general, doing so. It happens every day. It's always unfortunate, but how are the police supposed to know, in the seconds they have to respond, whether someone is a genuine threat or a nut-case acting out.

I didn't know the man, but I've known a few severely bipolar people, a couple of whom have taken their own lives. Don't discount the possibility that, on some subconscious level, this may have been a case of "suicide by cop".