President Joe Biden denounced white supremacy while addressing this weekend’s mass shooting at a supermarket in Buffalo, New York. The shooting, allegedly committed by a white teenager, targeted a supermarket in a predominantly black part of town. Speaking in front of victims’ families, local officials and first responders, Biden said “white supremacy will not have the last word” in America.

“White supremacy is a poison. It’s a poison running through… our body politic and it’s been allowed to fester and grow right in front of our eyes,” President Biden said Tuesday. “We need to say, as clearly and forcefully as we can, that the ideology of white supremacy has no place in America.”

18-year-old Payton Gendron was arrested at the supermarket and charged with murder. Before the shooting, he reportedly posted a document overflowing with racism and antisemitism. In the document, Gendron reportedly described himself as a supporter of Dylann Roof, who killed nine Black parishioners at a church in Charleston, South Carolina, in 2015, and Brenton Tarrant, who targeted mosques in New Zealand in 2019.

Biden also addressed the so-called “great replacement” conspiracy theory when discussing the Buffalo mass shooting Tuesday. The ideology, which is being investigated as a motivating factor in the shooting and has moved from white nationalist circles to mainstream discourse, alleges white people and their influence are being intentionally “replaced” by people of color.

“The Internet has radicalized angry, alienated, lost and isolated individuals into falsely believing that they will be replaced… by people who don’t look like them,” Biden said. “I call on all Americans to reject the lie, and I condemn those who spread the lie for power, political gain, and for profit.”

Biden’s condemnation of white supremacy is a message he has delivered several times since he became the first president to specifically address it in an inaugural speech, calling it “domestic terrorism that we must confront.” It’s unclear how Biden will try to accomplish this objective. Proposals for new gun restrictions have routinely been blocked by Republicans, and extreme rhetoric espoused on the fringes of the nation’s politics has only grown louder in recent months.

The Associated Press contributed to this report.