Haitian officials crucial to the investigation are now in hiding. Callers to Mr. Destin, the crime-scene officer, from blocked numbers have threatened his life and family, he said. Three other clerks and judicial officers on the case said they received the same calls. One colleague, tasked with interviewing suspects, left his lights on one Sunday night, then casually strolled away from his home with his wife, slipping into hiding with pages of handwritten notes from interviews with suspects, which haven’t yet been typed up.