Casually assigning psychiatric labels does a favor to who?  Indiscreet use of such labels only serves to dismiss a human being by stigmatizing rather than learning the individual's story and truly acknowledging their feelings and point of view.  It would be wise to avoid jumping to serious conclusions by writing someone off with an unqualified psychiatric label.

Who knows?  Perhaps the Vegas shooter, like others who committed similar acts, had been tarred with a "crazy" label and decided to take his resulting low self esteem and anger to the gun store.  Understanding and tolerance alway works better than stigmatizing labels and condemnation.  Peace.