The problem in New York City in 1964 and to a great extent today is that the NYPD has effectively criminalized the notion of coming to someone else’s aid.
As New York Mayor De Blasio has discovered the fact of life is that he answers to the NYPD. They do not answer to him.
The NYPD and too many police departments these days more closely resemble the paramilitary police gangs of Latin America than they do anything of the USA. They're not accountable to anyone else.
The Pink Floyd song, "Dogs of War", comes to mind with the part about how their masters don't control what they do.