Good discussion. One thing sometimes overlooked is a persons awareness level. One could be a very accomplished shooter, but if your awareness level is moot or low, it is dangerously easy to be behind the 8 ball in a violent engagement.
Sometimes you will not have a warning, but more than often perps will give off cues/body language that indicate high threats or striking posture.
Being able to recognize the body language and behavior sooner rather than later helps put you ahead of the curve when seconds count.