Earlier quoted context omitted.
There are plenty. People aren't evil by default. Give them more credit. http://www.ijreview.com/2014/03/125342-armed-man-gathers-peo... https://www.youtube.com/watch?v=yqkqzsIjujI http://bearingarms.com/concealed-carry-permit-holder-stops-s...
@ the last link: I don't think that would fit into the case of "preventing a crime", the guy shot 3 people then started leaving, before he got shot
However, continuing to extrapolate from this report, neither police (http://en.wikipedia.org/wiki/Tennessee_v._Garner) nor civilians are allowed to use lethal force on someone who's ceased threatening and is simply fleeing. If a case cannot be made that the threat was still there, guy who shot him should have been charged.