Considering the weakened state of the Outfit I don't think the Sicilian Mafia can be ruled out. Giacomo Ruggirello suddenly left everything to his Corleonese friend. Why? Did he have a debt to someone in Corleone? There are a lot of details that we aren't privy to, and without knowing all the facts I don't think we can presume that the Outfit was involved if this was organized crime-related.