He was named Joseph Augustus Zarelli. Just a quick look in Ancestry and its easy to triangulate who his parents likely were. It's all a matter of public record, nothing remarkable or secretive in this day and age. For sure they are dead; <modsnip: Removed info that could potentially identify the parents>
LE knows their whole family trees by now, and who is living and dead. They have already interviewed everyone they could. They are probably now hoping the press name release will nudge somebody with a conscience to come forward with information to indicate what happened and just finally confirm who was responsible. Although, I think we can reasonably surmise responsibility.
So, here's the crux. Where is the missing child report from 1957 that SHOULD have been filed by the parents?! Can you imagine the conversation between the parents? Husband to wife: "Honey, have you seen little Joe?" Wife to husband, "No, I thought he was with you. Oh well, never mind." And where were the relatives or neighbors to ask, "Hey, whatever happened to that four-year old son you had?"
One thing I have observed in historical situations in genealogical research is that many first generational new American families could be clannish and would close ranks and circle the wagons to outsiders regarding family issues. Silence and the passage of time often whitewash unpleasant family history. However, back when this child was murdered, the perp(s) had no comprehension that DNA would ultimately identify this boy in the end.