In your day to day life, you probably see lot of crimes happening...maybe at your work place, or at night while returning home from work etc. A robbery, attemt to murder, bombing, kidnaps anything.
Witnessing a crime is upsetting even if you weren't the victim. You may be worried about what will happen if you report what you have seen, so most of the times you decide to hide it within yourself. Has something ever happened in your life?