With the several deaths that have ensued at police hands recently, people aren't listening to the other side. They basically agree on the major points, they just see things... differently. Here is a video story out of Phoenix that was about a Black Rights Activist going through a live use of force scenario.
When I had a CCW license, I trained constantly. Marksmanship, practical pistol competitions and specifically what are called "shoot/no-shoot" scenarios. I used an air-powered simulation pistol with a narrow light beam and sensor in the barrel, with a system similar to the NES's Duck Hunt. You then watched a short video using a wall projector to simulate the exercise. When you pulled the trigger, the air piston would rack the slide (thus giving the feeling of firing a round) and flash the light. The projection screen would for 1-2 frames go black, except for a white spot to represent a proper target, generally the center of mass of the person(s) on the screen. If the weapon was aimed at the white spot, the light would reflect off of it and back to the sensor in the weapon and tell the computer to register a kill. The computer would then play the appropriate video clip based on if you were justified in shooting and if you hit or missed. If the person(s) on the screen made an aggressive move (such as advancing toward you and/or pulling a weapon) and you shot and hit, the video would show the person dropping. If you missed, they would shoot you and declare you "dead."
Sometimes the person would throw up his hands and surrender or run off without pulling a weapon. If shot then, you lost because your use of force was unjustified. Police officers make split-second life-and-death decisions every day. "Armchair quarterbacks" who have days or months to analyze what happened will 99% of the time find something that the officer missed in the 0.72 seconds the officer had to decide in who lived and died. The armchair quarterbacks can also kibbutz about "Why didn't you shoot the gun out of his hand?" or "You should have shot him in the leg to stop him instead of the head" are blowing smoke out their ass.
Unless you have had to make those kind of split-second decisions, be quiet. You have no idea what you are talking about and "should haves" are bullshit.