That the people in Kew Gardens heard the screams, but ASSUMED "someone else" would have already called the police.
New Yorkers may be insular and "not want to get involved", but geez, they aren't uncaring monsters. Not in 1964, not in 2013.
None of the witnesses observed the attacks in their entirety or saw the complete sequence. Most only heard portions of the incident without realizing its seriousness, and no witnesses directly saw the final rape and attack. But if true that the police were called after the first incident that a woman got “beat up and got up” and still didn’t arrive in time it could have been a breakdown with the NYPD’s inefficient telephone reporting system rather than the callousness of neighbors.