There were of course quite a few gang homicides during the 1950s, some of them getting a lot of publicity in the New York City media. Not all cases received equal attention, and it would also depend on if the defendants pled guilty or not. If they pled not-guilty, a trial would ensue and the case would be in the news for much longer, allowing the media to dig into the background of the defendants. If the defendants would plead guilty, they were sentenced and that was all that was basically reported on it (in most cases).
I take a look at three gang homicides on this website, with some pictures to go along with it. For instance, there was the infamous stomping and knifing of Michael Farmer, a boy from the Washington Heights section of Manhattan. His death resulted from a gang war over a pool in Highbridge Park. The newspapers made much of the fact Farmer was a polio victim.
Another case that got as much attention as the Michael Farmer killing was the trial of Salvador Agron and Luis Hernandez, the “Capeman” and “Umbrellaman” respectively. Sal knifed and killed two boys in a Hells Kitchen park in the summer of 1959 with Hernandez doing what he could to assist in the killing by using his sharpened umbrella-tip.
Although it is not in the exact era I am studying (1955-1959), another case that captured attention was a gang war between the Fordham Baldies from the Bronx and the Red Wings from East Harlem. In this case a man was killed and two teenagers severely injured.