[IRtorqued]

when I was teaching firearms marksmanship I started each and every session with these 4 bacis rules
1. every weapon is loaded until proven otherwise.
2. never place your finger inside the trigger guard until sights are on target and you are ready to fire.
3. never cover anything with the muzzle you do not intend to destroy
4. positively identify your target be aware of what is beside it and beyond it
once you pull the trigger you can never bring that bullet back
but you are most likely right there should never be any investigation into any police shooting, their self esteem may suffer and the last thing we need are more depressed cops.

[Ajnin]

Those rules work very well when you are at the range or are dealing with a compliant subject. Things don't go so smoothly when you have multiple perpetrators and innocent bystanders in a chaotic situation. It doesn't matter how well you are trained, in situations such as Columbine there can still be casualties of innocent people that are a result of police actions.