Rantaplane,
I don't think he much cared at the moment he made his choice.
One would hope, had he been confronted, that he would have seen the utter destruction he was about to heap on not only the people on the plane, but those left behind as well. Then again he was confronted, by the banging on the door, the screams from the back, yet he continued.
It remains cometely beyond my scope of understanding, how he could perpetrate such an act. The murder of innocent people, kids, babies.