CHARLOTTESVILLE, Va. (CBS19 NEWS) -- There are disturbing new details in the investigation of the Buffalo, New York super market massacre. 

The suspect was considering other targets, including elementary schools, churches, and Hasidic Jewish communities in New Jersey.

The suspect, 18-year-old Payton Gendron, believes in something called the "Great Replacement Theory." 

It's the belief spread by some far-right followers online that states a secret political group is working to replace white Americans with Black, Jewish, and Islamic people, and that violence and fear are the way to prevent this from happening.

Psychologist Dr. Mimi Arbeit believes that is what motivated the Gendron to attack.

“This conspiracy theory of 'you will not replace us' spoken by white supremacists in the attacks on Charlottesville in 2017,” said Arbeit, who is an expert on extremism.

"Great Replacement Theory” has been making headlines, especially after the racially-motivated shooting that left 10 people dead this past weekend.

A manifesto allegedly written by the shooter laid out specific plans to attack Black people and repeatedly cited "Great Replacement Theory." 

"'Great Replacement Theory' dates back centuries," said Arbeit. "We see these lies that were spoken at the propping up of the Confederate monuments in Charlottesville."

Arbeit is a professor at Suffolk University and says people become radicalized online, beginning to believe that they are somehow suffering.

"The idea that white people are being replaced is also a victimization narrative,” she said.

Arbeit explains that white supremacy is tied with fascism, which she says actually originated here in the United States.

"German fascists were borrowing ideologies from the U.S. So anti-Blackness is core to white supremacist ideology,” said Arbeit.

"Hate can have no safe harbor in America,” said President Joe Biden during a visit to Buffalo on Tuesday.

He met with the grieving families of the victims. 

"We have to figure out where this hate comes from,” added Biden.

Arbeit says to root out hate, people have to begin with their children.

According to the Anti-Defamation League, white supremacist propaganda has surged online, on the airwaves and in print.

In 2021, hateful propaganda appeared in every state except Hawaii, with the highest levels reported in Pennsylvania, Virginia and Texas.