It doesn't happen too often, but every once in a while the right person at the right place and time is present to subdue, rescue, or otherwise keep some bad thing from happening or continuing.

Recently, at a Lenexa, Kansas, BP gas station, a would be robber pulled a knife on the clerk. Unbeknownst to the robber, the clerk not only held a black belt in martial arts, but was also a former marine combat instructor. Let's just say the thief didn't stand a chance.

NBC Action News has the story: