Very sad and disturbing, but there is a reason behind nobody helping. It is the same reasoning that explained people's reactions to the NYC case that NvG posted. If you're around a group of people when something happens, and you don't see anyone else helping, you're far less likely to help yourself. Its something about being the first one to do something that the human psyche is reluctant to do. So the longer nobody helps, the less chance anyone is going to help.
So while it may seem sickening that nobody stopped to help, its an explainable behavior. However, the first van who apparently ran the child over on purpose and even the second van that ran over the child as well are just sick individuals.
The murdered woman's name was Kitty Genovese, here's the wiki page about the murder:
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