The Tulsa Race Massacre of 1921, in which a prosperous Black neighborhood in Oklahoma was destroyed and up to 300 people were killed, was not committed by an uncontrolled mob but was the result of “a coordinated, military-style attack” by white citizens, the Justice Department said in a report released Friday.

The report, stemming from an investigation announced in September, is the first time that the federal government has given an official, comprehensive account of the events of May 31 and June 1, 1921, in the Tulsa neighborhood of Greenwood. Although it formally concluded that, more than a century later, no person alive could be prosecuted, it underscored the brutality of the atrocities committed.

“The Tulsa Race Massacre stands out as a civil rights crime unique in its magnitude, barbarity, racist hostility and its utter annihilation of a thriving Black community,” Kristen Clarke, assistant attorney general for civil rights, said in a statement. “In 1921, white Tulsans murdered hundreds of residents of Greenwood, burned their homes and churches, looted their belongings and locked the survivors in internment camps.”

No one today could be held criminally responsible, she said, “but the historical reckoning for the massacre continues.”

The report’s legal findings noted that if contemporary civil rights laws were in effect in 1921, federal prosecutors could have pursued hate crime charges against both public officials and private citizens.

Though considered one of the worst episodes of racial terror in U.S. history, the massacre was relatively unknown for decades: City officials buried the story, and few survivors talked about the massacre.

The Justice Department began its investigation under the Emmett Till Unsolved Civil Rights Crime Act, which allows the agency to examine such crimes resulting in death that occurred before 1980. Investigators spoke with survivors and their descendants, looked at firsthand accounts and examined an informal review by the Justice Department’s Bureau of Investigation, the precursor to the F.B.I. In that 1921 report, the agency asserted that the riot was not the result of “racial feeling,” and suggested that Black men were responsible for the massacre.

The new 123-page report corrects the record, while detailing the scale of destruction and its aftermath. The massacre began with an unfounded accusation. A young Black man, Dick Rowland, was being held in custody by local authorities after being accused of assaulting a young white woman.

According to the report, after a local newspaper sensationalized the story, an angry crowd gathered at the courthouse demanding that Mr. Rowland be lynched. The local sheriff asked Black men from Greenwood, including some who had recently returned from military service, to come to the courthouse to try to prevent the lynching. Other reports suggest the Black neighbors offered to help but were turned away by the sheriff.

The white mob viewed attempts to protect Mr. Rowland as “an unacceptable challenge to the social order,” the report said. The crowd grew and soon there was a confrontation. Hundreds of residents (some of whom had been drinking) were deputized by the Tulsa Police. Law enforcement officers helped organize these special deputies who, along with other residents, eventually descended on Greenwood, a neighborhood whose success inspired the name Black Wall Street.

The report described the initial attack as “opportunistic,” but by daybreak on June 1, “a whistle blew, and the violence and arsons that had been chaotic became systematic.” According to the report, up to 10,000 white Tulsans participated in the attack, burning or looting 35 city blocks. It was so “systematic and coordinated that it transcended mere mob violence,” the report said.

In the aftermath, the survivors were left to rebuild their lives with little or no help from the city. The massacre’s impact, historians say, is still felt generations later.

In the years since the attack, survivors and their descendants and community activists have fought for justice. Most recently, a lawsuit seeking reparations filed on behalf of the last two known centenarian survivors was dismissed by Oklahoma justices in June. In recent years, Tulsa has excavated sections of a city cemetery in search of the graves of massacre victims. And in 2024, the city created a commission to study the harms of the atrocity and recommend solutions. The results are expected in the coming weeks.