© AP file Almost from the start, the federal investigation was frustrated by a wall of silence on the part of local residents. White residents didn’t want to be interviewed because they wanted to protect their own while black people lived in a state of constant fear, afraid of sharing even the most minor details. From the killers’ perspective, this wall of silence reinforced the notion that blacks could be abused, tortured – and even murdered – with impunity. In all likelihood, the perpetrators became confident that details of the story would only grow fainter as the facts of the crime were gradually forgotten. Local police did not even launch an investigation into the murder of the Malcolms and Dorseys. On all four death certificates, the coroner wrote the bureaucratic phrase that, for years, had been listed as the cause of death for victims of lynchings across the country: “At the hands of persons unknown”.