Editor’s Note: This article has been amended to clarify the extent of assistance and information Rebecca Solnit provided Thompson and The Nation.

In the months after Hurricane Katrina, word began to circulate that armed white men in New Orleans had opened fire on African-Americans seeking to flee the floodwaters. These stories were dismissed as paranoid thinking, lumped in with tales of man-eating alligators and government officials who had conspired to flood the Lower Ninth Ward. One man, Donnell Herrington, who said he’d been the victim of such a shooting and had the scars to prove it, was shown on video by Spike Lee in When the Levees Broke, whose New Orleans premiere Mayor Ray Nagin attended. Still no police–or reporters–chose to pursue the matter.

Two years ago A.C. Thompson did. He began with a tip from author Rebecca Solnit; while researching her new book A Paradise Built in Hell, she’d come across a pattern of evidence, including footage of white Algiers Point residents boasting that they’d shot people and several witnesses who’d either heard murder confessions or seen bodies of what appeared to be murder victims. Solnit first approached two Pulitzer Prize-winning reporters, but only Thompson, who’d cut his teeth at Bay Area alternative weeklies, sensed a stunning story. With support from The Nation and The Nation Institute’s Investigative Fund, where I am an editor, he took several reporting trips to New Orleans. Most victims and potential witnesses had been displaced and were nearly impossible to find; police officers refused to talk, out of fear of retaliation. But one person at a time, Thompson reconstructed a chilling chain of events for his January 5 Nation articles.

What he found in the end was evidence, culled from emergency room doctors, victims, shooters, witnesses and autopsies obtained through an Investigative Fund lawsuit, that at least eleven African-Americans were shot by white vigilantes, some shouting racial epithets; several may have been killed. In another gruesome incident, shooting victim Henry Glover was left to bleed to death while his would-be rescuers were handcuffed and beaten by local police. Herrington was chased by vigilantes shouting, “Get that nigger!” as they pounded him with buckshot. It was as if Thompson had uncovered a scene from an earlier time–1925 or 1955, not 2005.

“Victims, perpetrators, witnesses–nobody in law enforcement had ever spoken with them,” Thompson recalls. “It was mind-boggling.” The New Orleans Police Department had not initiated an investigation into a single case.

As we reach the fourth anniversary of Hurricane Katrina, arrests may finally come about, through federal law enforcement: the FBI has opened an investigation into the Glover case, and in May federal prosecutors empaneled a grand jury to look into the possibility that police officers shot him and destroyed the evidence. In early August, FBI agents raided an NOPD office and seized files and a computer hard drive from a homicide detective assigned to investigate the death. Herrington tells The Nation that he, too, was interviewed by the FBI, indicating that the probe has gone beyond the Glover case to encompass the broader pattern of post-Katrina violence. Thompson, who continues to report on the vigilante attacks for ProPublica, says FBI agents have interviewed other people from the neighborhood as well.

But in New Orleans, the wheels of justice have rusted. After Thompson’s story broke last December, the NOPD announced it would open an investigation. But according to Herrington, as of late August, the police have yet to interview him about the case. “My life is important to a lot of people. I mean something in this world,” Herrington said. “For me to think the guys who shot me got away with it, it makes me angry and it makes me feel bad.”