Was this hyperbole or honesty? Drawing a firearm is a deterrent and is employed in order to prevent things to escalating to a point where an officer has to fire.
So, going from what seemed like an ordinary traffic stop to looking down a gun, I figured he was prepared to kill me if he found it necessary. As I could not figure out any reason for him to want to stop me like that in the first place, it seemed logical there was some massive escalation I was unaware of.
I am not certain about the exact distance but I think a hostile person brandishing a knife within 20 or 25 feet is considered to have an advantage / pose serious risk of death (able to inflict serious trauma) over an officer with a holstered weapon. (In NYS)
Of course its a deterrent, but the only thing that makes it more of a deterrent than a whistle is that the officer is (or presumed to be) ready to shoot.
Police have their own rules.