On May 31, 1921, white men with weapons waited outside a Tulsa, Oklahoma, courthouse. Inside, a 19-year-old black shoeshiner named Dick Rowland was being detained for allegedly attacking a white elevator operator. Fearing that Rowland would be lynched, black men armed themselves and showed up at the courthouse to counter the white men’s show of force. Soon enough, a fight broke out. Outnumbered, the black men retreated to Greenwood—then a thriving black neighborhood known as Black Wall Street—and the white men took chase.

What followed was a bloody massacre that continued on into the next day. The racially motivated incident killed more than 300 black Tulsans and displaced an estimated 10,000. Before it was all over, at least 35 city blocks burned to the ground. Survivors recounted stories of bodies being tossed off bridges and into unmarked mass graves. Now, reports DeNeen L. Brown at The Washington Post, Tulsa Mayor G.T. Bynum has announced plans to investigate those accounts by searching for the unmarked graves.

“We owe it to the community to know if there are mass graves in our city,” Bynum tells Brown. “We owe it to the victims and their family members. We will do everything we can to find out what happened in 1921.”