I am trying to address the idea of perception. In the actual case that happened the guy coming around the corner was a handcuffed DUI suspect who was attempting to escape the shooter.....He was shot, tragically. The officer however was cleared of any wrong doing based on his perception of the situation in that split second of a "rapidly evolving, tense situation" (Graham v Connor)not the "clear 20/20 hindsight" of the actual situation. And that is my point- officers have to make split second decisions based on what they know (perceive)in that split second. If you don't know what they officer believed at the time you can't possibly decide if the action was reasonable or not.