Person A wakes up in the morning. Decides to be a parasite. To forcefully take something that does not belong to them. They did it yesterday and will do it tomorrow. That person chose the wrong shop and gets gunned down by a brave citizen.
Person B wakes up in the morning. They are a tax paying citizen with a stable job. A job that is critical for the well functioning of society, an honorable profession. They encounter someone and they fuck up. With their blood pounding in their ears as their heart rate sky rockets they make a horrible decision due to the very real fear that a suspect was reaching for a weapon.
That's the scenario that I see before me Enoch. That's why juries have a hard time convicting someone on a bad shoot. Cops do go to prison for crimes here is an example:
http://www.nytimes.com/1994/07/12/us...ed=all&mcubz=1
Deliberate acts of evil are punished while heat of the moment fuck ups are viewed in a different light.