The Double Life of a Don

His name was Aniello Dellacroce, which in Italian means "little lamb of the cross," and he took pleasure in killing people. "He likes to peer into a victim's face, like some kind of dark angel, at the moment of death," a federal agent once said of the Mafia chieftain. As underboss of the Gambino clan, the most powerful of New York's five families, he was a member and chief enforcer of "the Commission," the 11-member council that reputedly oversees organized crime around the U.S. Occasionally disguised as a priest under the alias of Father O'Neill, a play on his first name,...