The first-ever U.S. Justice Department review of the 1921 Tulsa Race Massacre concluded Friday that while federal prosecution may have been possible a century ago there is no longer an avenue to bring a criminal case more than 100 years after one of the worst racial attacks in U.

A new federal review finds the 1921 Tulsa Race Massacre was the result of systematic, racially motivated violence targeting Black residents of the city’s Greenwood District.

The Justice Department’s conclusion follows an investigation of the 1921 atrocity in Oklahoma in which up to 300 Black residents were killed.