Probable copycat attack
News of cutting throats on the aircraft has been all over the place, this guy probably got it in his head and took it from there. I think this was an isolated case of a maniac doing his best to imitate that which he didn't have a clue about doing.
Who knows how empty the sky is
In the place of a fallen tower.
Who knows how quiet it is in the home
Where a son has not returned.
-- Anna Akhmatova (1889-1966)