Eugene Williams, a 17-year-old black boy, was stoned to death by white people in 1919 after he swam into what they deemed the wrong part of Lake Michigan.

In response, black people in Chicago rose up in protest, and white people attacked them. More than 500 people were injured and 38 were killed. Afterward, the city convened a commission to study the causes of the violence.

The commission found “systemic participation in mob violence by the police,” Khalil Muhammad, a professor of history, race, and public policy at Harvard Kennedy School and author of the book The Condemnation of Blackness: Race, Crime, and the Making of Modern Urban America, told Vox. “When police officers had the choice to protect black people from white mob violence, they chose to either aid and abet white mobs or to disarm black people or to arrest them.”

In the process of compiling the report, white experts also testified that “the police are systematically engaging in racial bias when they’re targeting black suspects,” Muhammad said. The report “should have been the death of systemic police racism and discrimination in America.”

That was in 1922.

It’s almost 100 years later, and thousands of Americans are in the streets daily, protesting the same violence and racism that the Chicago commission documented. It may seem like nothing can change, but Muhammad said the last several weeks could be a wake-up call for some Americans to what policing in this country really means.

Part of that awakening, though, also involves understanding the history of police violence. Muhammad’s work focuses on systemic racism and criminal justice; The Condemnation of Blackness deals with the idea of black criminality, which he defines as the process by which “people are assigned the label of criminal, whether they are guilty or not.” That process has been a vicious cycle in American history, Muhammad explains, wherein black people were arrested to prevent them from exercising their rights, then deemed dangerous because of their high arrest rates, which deprived them of their rights even further.

I spoke with Muhammad by phone to better understand this history, what it means today, and what it would take to make 2020 and beyond different from 1922. A transcript of our conversation, lightly edited for length and clarity, follows.