The Tulsa Historical Society and Museum seems a good place to start:

>On the morning of May 30, 1921, a young black man named Dick Rowland was riding in the elevator in the Drexel Building at Third and Main with a white woman named Sarah Page. The details of what followed vary from person to person. Accounts of an incident circulated among the city’s white community during the day and became more exaggerated with each telling.
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>Tulsa police arrested Rowland the following day and began an investigation. An inflammatory report in the May 31 edition of the Tulsa Tribune spurred a confrontation between black and white armed mobs around the courthouse where the sheriff and his men had barricaded the top floor to protect Rowland. Shots were fired and the outnumbered African Americans began retreating to the Greenwood District.
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>In the early morning hours of June 1, 1921, Greenwood was looted and burned by white rioters. Governor Robertson declared martial law, and National Guard troops arrived in Tulsa. Guardsmen assisted firemen in putting out fires, took African Americans out of the hands of vigilantes and imprisoned all black Tulsans not already interned. Over 6,000 people were held at the Convention Hall and the Fairgrounds, some for as long as eight days.
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>Twenty-four hours after the violence erupted, it ceased. In the wake of the violence, 35 city blocks lay in charred ruins, more than 800 people were treated for injuries and contemporary reports of deaths began at 36. Historians now believe as many as 300 people may have died.

A commission appointed by the state government reported in 2001 that:

>Black Tulsans had every reason to believe that Dick Rowland would be lynched after his arrest. His charges were later dismissed and highly suspect from the start..... As hostile groups gathered and their confrontation worsened, municipal and county authorities failed to take actions to calm or contain the situation.
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>At the eruption of violence, civil officials selected many men, all of them white and some of them participants in that violence, and made those men their agents as deputies.... In that capacity, deputies did not stem the violence but added to it, often through overt acts that were themselves illegal. Public officials provided fire arms and ammunition to individuals, again all of them white.
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>Units of the Oklahoma National Guard participated in the mass arrests of all or nearly all of Greenwood’s residents, removed them to other parts of the city, and detained them in holding centers.... Entering the Greenwood district, people stole, damaged, or destroyed personal property left behind in homes and businesses. People, some of them agents of government, also deliberately burned or otherwise destroyed homes credibly estimated to have numbered 1,256, along with virtually every other structure — including churches, schools, businesses, even a hospital and library — in the Greenwood district..... Although the exact total can never be determined, credible evidence makes it probable that many people, likely numbering between 100-300, were killed during the massacre.
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>Not one of these criminal acts was then or ever has been prosecuted or punished by government at any level: municipal, county, state, or federal.