The only thing we know is that the whole family (two parents and a baby) are dead. The baby's corpse is not found. All details were provided by the killer couple. So the killer couple had a strong motive and a long time to make a story that would minimize their guilt. It is hard for me to figure out how two people could kill two other people easily without planning in advance. How the baby died is anybody's guess. By exposing the baby's death, the killer couple would have faced criminal charges and civil lawsuit from the young couple.
The crime could have a different scenario. The killer couple probably set a trap for the young couple. The killer couple invited the young couple to their home by pretending the baby was still alive or the killer couple might not tell the young couple there was a problem with their baby. Trap was set and weapon was ready. The young couple was probably killed without any knowledge of their baby's fate. So this could be a more sinister crime than what the article presented and truth would never be revealed.
