They probably do have headstones or records somewhere.
You might be able to find out when they were released if you search under inmates, new york. The difficulty will be that I do not know the birthdates of these men and there are people of the same name in the same area. New York did have a parole board at that time or shortly thereafter. It looks like the murder was an aside to what they were trying to do, so they could have grounds for non premeditated.
Good luck.