A startling crime committed in the 1960s highlighted a very complex issue in society, which peaked the attention of John Darley and Bibb Latane, who conducted in-depth studies about the phenomenon now known as Bystander Effect.
The following documentary features Darley explaining the background of the death of Kitty Genovese, the relevant study and its implications:
Bystander Effect is observed not just when other people are in danger, but also when the subject themselves are in potential danger, as shown in this clip: