[saghul]

In my last year of university I had a class on ethics and I learned the case of Kitty Genovese, a woman who was stabbed to death in New York. Many people watched but nobody helped.

This "phenomenon" is called "dilution of responsibility", that is, people don't do anything, because nobody else is doing it. I guess what you observed was exactly this.

Found a link describing the case here: http://www.talsico.com/newsletters/newsletter6.htm