US President Joe Biden became the first president to commemorate the 1921 Tulsa race massacre Wednesday. The incident is one of the worst race-related crimes in American history, involving the murder of hundreds of black Americans 100 years ago.

Biden called the incident “a massacre” and said that silence was not an option. The chief executive recounted the incident where the number of those killed remained undetermined.

“This was not a riot. This was a massacre. I come here to help fill the silence. Because in silence, wounds deepen. And only, as painful as it is, only in remembrance do wounds heal. We just have to choose to remember,” Biden said.

The Oklahoma legislature established a commission to investigate the massacre in 2001. The commission said it had confirmed around 39 victims of the two-day incident but estimated that the true number could be up to 300.

The incident occurred on May 31 and June 1 in 1921. It began with the arrest of a black American shoe shiner who was accused of assaulting a white female elevator operator. The incident sparked a riot that was partly led by the Ku Klux Klan. Approximately three dozen blocks of the Greenwood district – called the “Black Wall Street” – was burned to the ground.

The commemoration of the event has gained public attention following a year of racial strife triggered by the murder of George Floyd by Minneapolis police officer Derek Chauvin.

“We do ourselves no favors by pretending none of this ever happened, or it doesn’t impact us today, because it does still impact us today. We can’t just choose to learn what we want to know, and not what we should know. We should know the good, the bad, everything. That’s what great nations do, they come to terms with their dark sides,” Biden said.