President Joe Biden decried a mass shooting at a Buffalo grocery store as an act of domestic terrorism on Tuesday, joining a slate of New York officials denouncing a tide of white supremacy they fear has become mainstream.

“What happened here is simple and straightforward: Terrorism,” said Biden, who appeared at a local community center alongside prominent elected officials.

The attack on Saturday left 10 dead and three others injured. Eleven of the shooting victims were Black. Officials said the shooting was being investigated as a hate crime by both local and federal law enforcement.

Payton Gendron, the suspected 18-year-old shooter, was accused of authoring a racist document online that centered on the conspiracy theory that white people are being “replaced.” The suspect, who is white, allegedly live-streamed the shooting on the social media platform Twitch.

The suspect is a resident of Conklin, New York, a town outside of Binghamton, hours away from Buffalo. Biden sounded off on a slate of mass shootings to occur in recent memory and called for stronger action against rooting out white supremacy in its tracks.

“White supremacy is a poison,” he said, interrupted by applause from the crowd. “It's a poison … running through our body politic that's been allowed to fester and grow right in front of our eyes.”

Biden was joined by elected officials from New York, including Sen. Majority Leader Chuck Schumer (D-NY) and Gov. Kathy Hochul, a Democrat from Buffalo. Hochul said the same sentiments embraced by the accused shooter were becoming commonplace, even within Congress, without explicitly naming which members she was referring to.

Social media posts from U.S. Rep. Elise Stefanik (R-NY) that her campaign paid to promote on Facebook have been scrutinized in the aftermath of the shooting, as critics say they touted the same “great replacement” conspiracy theory seemingly embraced in the shooter’s online writings.

Stefanik and her allies have vociferously denied the connection, with Senior Adviser Alex DeGrasse saying in a statement Monday that Stefanik “has never advocated for any racist position or made any racist statement,” calling the shooting “an act of evil.”

“These hateful philosophies are starting to become mainstream, and they took hold in the mind of an 18-year-old who lives three hours from here,” the governor said. “And he targeted this community — intentionally coming to this zip code … he was targeting and wanted to execute black New Yorkers. That's hard to comprehend.”