SACRAMENTO, Calif. (KTXL) — Law enforcement said the man, suspected of killing 10 people and injuring three others at a Buffalo supermarket, had written a 180-page manifesto, illustrating his fear that white Americans may one day be replaced by people of color —a nationalist conspiracy known as the Great Replacement theory.

“Really a false, again idea, that there are a group of elitists people, often Jewish, and sometimes Democratic party, seeking to really overturn the demographics of the United States on purpose to bring immigrants to the U.S. in order to overtake the white population,” Rachel Carroll Rivas said. “And then there’s this call to arms within this conspiracy, that white folks need to act to prevent this.”

Rivas, of the Southern Poverty Law Center, warns that perpetuating such a warped theory only motivates further acts of violence.

“It is a false, white supremacist, racist conspiracy theory. It is not the truth, and this idea has motivated, unfortunately, a number of violent mass killings around the globe in the seven or so years,” Rivas said.

Political Republican consultant Tab Berg of Berg Communications said this shooting cannot be simply characterized as a result of a replacement theorist.

“This kind of pop psychology is actually incredibly damaging to any kind of a realistic effort to help address mental health issues. When somebody is in some kind of a psychotic episode — you can’t even go out and kill a bunch of people unless you’re in some kind of deep mental distress,” Berg said. “You’re going to find anything to latch onto. And for us to distract from that reality, means we’re not going to address that solution, which is severe mental health issues.”

“This is not about guns, this is not about replacement or immigration. This is about mental health,” Berg said.

Rivas said we all need to take responsibility if real change can come about.

“Online, on the media, on the mouths of elected officials, we have people that are being manipulated and we are all responsible for interrupting that, and calling it and saying that this is not OK,” Rivas said.