Gotta give props to the guy asking him to let everyone ELSE go.
As far as asking why nobody shot this guy right away, ask a cop. Do you think that any law enforcement officer WANTS the death of another human being on their hearts? Until the guy fires the gun himself, theres no way to tell if its even a real gun. The man was obviously mentally ill. To an extreme I hope no one here ever has to witness.
The security guard who shot him was an ex-police officer. He acted in a way that shows restraint and training. What if he had fired at the man as soon as he entered the room full of people, and the bullet struck a fleeing civilian? What if he waited until most of the people were gone, and fired on the man and injured/killed one of the board members sitting a couple feet away?
For all he knew, the man could've had a water gun. When dealing with severly mentaly ill people, rash decisions can oft times be more dangerous than the person with the gun.
Im just glad no innocent people were hurt. Maybe if we lived somewhere that actually cared about the mentally ill, this all could've been avoided.