The guards had a tradition to live up to. Kitty Genovese is lonely and forgotten in her grave. So like true New Yorkers from the 1960s, they looked the other way.
I've lived in new York City all but one of my 63 years, and there are still plenty of people here today that would rush to help someone being attacked like that. These days, the past few decades or so, it would most likely be Puerto Rican guys helping. There are hardly any white guys here anymore worth a schiff in this regard.
The Kitty Genovese incident I believe happened in the 70s, when a racist black guy, specifically sought out a white woman to attack. It was in the Kew Gardens section of Queens. Fortunately for the attacker, she was no relation to "Vito".