To be honest, I think Alec Baldwin has pulled the trigger on sets before like this.. That's why he repeats it twice. "When I first got in this business, I was trained not to just go click click click and pull the trigger, etcetera..because even if it's incremental, you damage the firing pin."
So, he says that part like he's been told not to do this before.
So, of course, he does it again to someone who's trying to tell him what to do.. not the director telling the producer what to do, but a cinematographer telling the director, lead actor, what to do...
And, my theory, she shot him down, possibly, or he just didn't like a low level crew member telling him what to do...
In any event, this guy is a spoiled brat who's never dealt with consequences, like so many other Hollywood brats. And he's obviously, a narcissist who doesn't have any empathy for others.