The two teenagers suspected of killing three Muslim members of the San Diego Islamic Center Monday idolized prior perpetrators of such white supremacist attacks, according to a 75-page manifesto they allegedly wrote that's circulating online.
The pair said they believed in right-wing conspiracy theories about immigrants and Jewish people and sought to replicate the 2019 Christchurch, New Zealand shooting where 51 Muslims were killed at two mosques.
The manifesto and videos apparently filmed by one of the alleged shooters haven't been independently verified by KPBS but experts said there's little doubt as to their authenticity.
KPBS is not publishing the manifesto, videos or naming the alleged suspects, aged 17 and 18.
The materials from the alleged shooters was shared on a Discord server then posted on another forum online, according to Jared Holt, a senior researcher at Open Measures who monitors the spread of extremism and other harmful content online.
"We came across the alleged manifesto on a forum that I will not give publicity to on the news here, but it was from a community that is fairly adjacent to a lot of spaces where this idolatry and almost worship of mass killers takes place," Holt told KPBS Tuesday.
The FBI said at a news conference Tuesday it is investigating the manifesto and videos.
There's little doubt that ideology played a role in motivating Monday's violence and that the suspects sought to pay homage to the 2019 Christchurch shooting, Holt said.
"They sought to replicate one of the deadliest racist mass shootings in history, and they sought to do it in the U.S. as tribute to that shooting," he said. "I think the ideology is inseparable from the violence.
The two suspects were well versed in white supremacist ideology, said Heidi Beirich, the cofounder of the Global Project Against Hate and Extremism.
"It does appear as though this was more than just some online role-playing," Beirich said in an interview. "Because the manifesto dives very deep into white supremacist killers (and) white supremacist books."
Both suspects appear to have contributed to the manifesto. In it they blame Muslims, Jewish people, immigrants, women, the LGBTQ+ community and the left for seeking to destroy white culture.
They also repeat the white supremacist Great Replacement Theory which says there’s a conspiracy to bring in nonwhite immigrants to end the country’s white demographic majority.
Some conservatives have helped mainstream the theory, including Tucker Carlson and Elon Musk.
Holt says anti-immigrant and anti-Muslim rhetoric from conservative politicians and media figures plays a role in fostering hateful ideologies.
"Hate is a very animating emotion in a lot of people and I think today's conservative movement has really tried to exploit that for their own political gains," Holt said.
The Trump administration has justified its immigrant crackdowns and its travel ban for majority-Muslim countries as matters of national security.
In December conservative influencers spread conspiracy theories about Somali immigrant-run childcare centers in Minneapolis. In January, some began showing up at childcare centers in San Diego.
President Donald Trump questioned why so many immigrants to the U.S. come from majority-Muslim countries instead of white-majority countries in a speech at a December Pennsylvania rally.
"We always take people from Somalia, places that are a disaster, right?" Trump said. "Filthy, dirty, disgusting, ridden with crime. The only thing they’re good at is going after ships."
Beirich says it's dangerous for political leaders to demonize marginalized groups of people.
"You are sanctifying lies about this community, which opens them up to hate crimes and terrorism," she said. "It's really dangerous, and it makes it seem like these ideas are legit when they're not."
Young people can come across extremist ideas on mainstream social networks such as Instagram and TikTok, Holt said. But the communities that celebrate and revere white supremacist mass shooters are more niche — they would need to seek them out intentionally.
"What a lot of these communities have figured out in recent years is if they brand themselves as true crime fans, they can last a little longer (on moderated platforms) or potentially evade detection," Holt said.
Within those communities, Holt said, themes quickly start to overlap with hate, extremism, extreme violence and gore.
"A lot of these spaces are sharing shocking and offensive content ... to kind of give each other their kicks," he said
The way young people engage on social networks online is also changing, he said.
"A lot of younger people online are having almost kind of a passive experience with it, where they're consuming the content, they're joining communities ... and seem to be less drawn to this idea of being the main character of their Facebook page or whatever," he said.
By not actively posting hate-related content, radicalization may be more likely to go undetected.
There are signs a teen or young person may be engaging with these communities, Holt said, such as secretive and anti-social behavior and self-isolation.
They may also pick up interests in stories about violence and mass shootings.
Editor's note: In line with industry best practices, KPBS will avoid naming the suspects in the shooting. Research shows that focusing on mass shooters can inspire copycat violence and glorify their actions. KPBS will focus its reporting on the victims, survivors and the community.
