At what point can you fire?
Assuming that I really had a good reason to pull the gun, ie. I evaluated the situation and under my best knowledge I found that a life is in danger, I'd shoot immediatelly after he ignored the first warning.
However I'd never draw a gun when not in a real danger. I believe that posing with a gun - or even worse, thinking that a gun is some kind of a human remote control - is the worst error one can do. I mean a gun is a tool for killing things and one should never pull it if s/he is not in a situation when killing is morally justified (for our moral and experience is the only things we can use to make our decisions namely in a danger).
For me, a handgun is a last line of defence. For other than openly life threathening situations I'd rather use bare hands, telescopic batton or cajune pepper spray.