Don't threaten people with a weapon or a fake firearm unless you are ready to deal with what can happen next.
Think the guy went a little over the top but if he was ex military they taught us when in doubt, keep shooting. Under stress that repetitive training kicks in.
The shooter demonstrated a lack of awareness about his surroundings that I think the ex-military/ex-LE possibility has already been dismissed.
(I'm not judging the guy's shooting skills; I am only pointing out what others already have: He had his back turned to other patrons for too long.)