Well, I just remembered some things:
1) When I was in college, my suitemate's boyfriend saw some people in a parking lot trying to steal a car. He chased them and was shot. I think they were eventually arrested, but I don't remember. My suitemate, understandably, was a major advocate of increased campus security after that.
2) Some years ago in my own current neighborhood, I was walking home from a park and happened to pass a woman wheeling a baby in a stroller. She had a dog with her, and slammed the dog up against a fence and began screaming and cursing at it. There is a police station nearby. There may not have been much, if anything, the police could have done, but I was scared of the woman and for the baby and the dog. However, I didn't report the incident, and to this day I am ashamed that I did not.