One of my favorite quotes, Dotti, is from the book Dune: "Fear is the mind-killer." Sometimes, though, fear can be what saves your life.

I once sat next to an LAPD officer on a plane. He told me that his job was very strange (he came to it later in life than most). Most of the time, cops are sitting around waiting for something to happen. When something does, a situation like a man in the street waving a gun around, it's the cop's job to take it away from him when one's natural instinct is to get the hell out of there.

Cops are subject to long periods of inactivity punctuated by bursts of high alert and action. I can see where this situation might lead to overreaction. Another impact on citizens' reluctance to intervene is the fear of being sued. It always comes down to protecting oneself first rather than helping others. That's why heroes are so thin on the ground.