The 180-page letter being attributed to a white supremacist charged in Saturday’s shooting rampage that targeted African-Americans at a Buffalo grocery reads like an operational manual for others to copy, said an expert on domestic terrorism and extremism. He believes parts of the document were plagiarized, KTLA sister station WIVB reported.

Federal authorities continue to investigate the hate-filled document.

An 18-year-old teenager surrendered at the scene and is charged with the mass shooting at the Tops market on Jefferson Avenue that left 10 people dead and three more injured.

The teenager wore military-style clothing, including a bulletproof vest, and the screed states that he used a Bushmaster XM-15, a weapon used by fighters in the Iraqi Civil War against ISIS. He had been seriously working on his violent plan since January, the screed states, but he spent years buying ammunition, surplus military gear and practicing shooting.

Jon Lewis, a research fellow for the Program on Extremism at George Washington University, said individuals who commit these acts of racism not only want to be memorialized, but they also want like-minded people to copy the horrific acts of violence.

“They want individuals to say, you know what, if this guy can do it with a couple thousand dollars and a map of the store and no real training and whatever, then so can I,” Lewis said. “The goal for individuals like this is violence and they’re often not really picky with who does it, they just want more violence because, in their minds, violence begets violence, violence leads to more violence, and they are all hoping to be the ones who kind of do the most violence to start what they view as the collapse of the whole system.”

Lewis said the author of the document plagiarized portions of a similar screed written by the perpetrator of the 2019 Christchurch mosque shootings in New Zealand.

The document allegedly belonging to the Buffalo shooter, which was obtained by WIVB, describes in chilling detail how the attack would be carried out and that the racist shooter chose the Masten District Tops grocery because it was the closest neighborhood in New York with the highest percentage of Black residents.

The ZIP code 14208 is almost 80% Black, and the shooter traveled more than three hours to kill as many Black people as he could, the screed states. The author also wrote that he chose a neighborhood in New York because of its “heavy gun law,” which helped “ease” him knowing that anyone legally armed that he might encounter during his rampage would be limited to a maximum of 10 rounds.

The document includes a hand-drawn sketch of the grocery and details of how he would livestream the massacre, which he did on Twitch, a streaming platform popular with gamers.

“If you read the manifesto, he intended to make sure that other people would see what happened in real time here so they would consider other acts as well,” said Gov. Kathy Hochul. “That’s what has to shut down right now.”

The screed mentions how the shooter planned to leave the grocery and drive south on Jefferson Avenue to shoot more random Black people on the streets. The document is riddled with white supremacist notions, including the so-called great replacement theory embraced by far-right talk show hosts such as Fox News’s Tucker Carlson and politicians such as U.S. Rep. Elise Stefanik and JD Vance, the Republican nominee to represent Ohio in the U.S. Senate.

Lewis said the great replacement theory is a white supremacist idea that Jewish people are conspiring around the world to replace the white, European race with non-whites.

“And it ties into the debate around immigration, around gun control, around antisemitism and it’s important to think of all those kinds of pieces as pretty connected, and these are all things as the manifesto indicates that clearly motivated this individual to action,” Lewis said.

“And so when you look at his postings online on Discord and in several other places, you see this kind of continued path from around the time Covid started all the way through the attack where he is increasingly online, he’s increasingly in these spaces that again foster these extreme viewpoints and show individuals that this kind of rabbit hole that goes deeper and deeper and deeper where all the sudden you’re at the end of it and you think, you know what, the great replacement theory is probably true.”

The U.S. Justice Department said it is investigating the incident as a hate crime and act of racially motivated violent extremism.

U.S. Attorney General Merrick Garland vowed to conduct a “thorough and expeditious investigation into this shooting” and seek “justice for these innocent victims.”