I think the point Amsdorf is making is more along these lines:
http://www.kxly.com/news/Bystander-H...w/-/index.html
It is interesting when I went looking for this incident, the first 5 news reports just said the person that stopped the robbery just yelled at the robber and he fled...no mention that the yell was "drop that knife or I'll shoot!" or even the fact that the good Samaritan was armed.