At all costs, read Masaad Ayoob's account of the Miami86 FBI shooting.
Failing that, John Ross's account in "Unintended Consequences" is pretty good...it's a distillation of several sources, and contains good details on several others. But Ayoob captured the mental workings of a wounded FBI agent firing a revolver one-handed against a pair of seriously dangerous lunatics who'd just wounded or killed several other agents. Basically, under the extreme stress, this one agent focused down into a "machine" capable of doing nothing other than reloading, advancing on the target, doing sight alignment and trigger pull. Someone else walking up had to stop him from endlessly clicking the dry gun after it was all over. His hearing was shot, just before his "final charge" one of the crooks had unloaded on him from close range, missing...the agent literally never noticed, he was too busy reloading. He had tunnel vision, his sense of time perception was radically skewed.
But he won. Understanding his brain under those circumstances will take you a long way towards being able to write some really edgy stuff.
These effects are by no means universal. Under certain surprise ambush circumstances, people can get seriously, radically confused, and can panic. Fatally so. See also Ross's account of the first moments of the BATF's raid on Waco...not the final burning, the initial assault weeks earlier.
The sense of "time compression" and "tunnel vision" I can personally attest to, once in a combat situation, albiet with no guns involved. I've never drawn, threatened with or fired a gun in anger, I've never had to use deadly force. I've backed street assailants down with knives twice. Most of my comments above is based on "book learning", versus experience.
Based on reading and my sole serious combat incident, I'll say this: the guy that survives quickly spots the danger he's in, and goes into an "overdrive" state of heightened concentration and speed, with time compression "mental effects" going on. He'll then react quickly and decisively to counter the threat, taking the baddies totally by surprise and "mentally disarming them" before weapons use or other force is even a factor.
Even if you make a tactical error in your "sudden response", it *probably* won't matter because of what you've done to the opponent's mental state. But do try not to screw up
. In my case I charged four murderous loonies and shoved them off a downed victim while failing to note their claw hammers being used as weapons. Big screwup...but they were too surprised to think about clobbering me, since I got the hell back the moment the victim the was clear
. Physically, they could have...mentally, nope, not in the 2 seconds tops I spent in close range.
An energetic mistake "right now" can still win over a slow reaction...but note my use of words like "can"
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Jim