After two mass shootings in under 24 hours claimed 31 lives so far in El Paso, Texas, and Dayton, Ohio, the Southern Poverty Law Center's Intelligence Project Director Heidi Beirich tells Business Insider that hate-driven violence is to blame for the majority of domestic terrorism in the US.

Beirich says President Donald Trump has encouraged white supremacist violence and that the GOP and the Trump administration must stop "fueling" white supremacy and "call [Trump's language] for what it is, which is either racist or anti-immigrant."

She also told INSIDER that White House Chief of Staff Mick Mulvaney's comments on addressing the link between mass violence and social media was "dodging the issue here, which as the tech world knows this is a problem and is trying to fix it for the most part, the President of the United States is fueling it."

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Two shooters opened fire in El Paso, Texas, and Dayton, Ohio on Saturday and Sunday, killing 31 so far in attacks that occurred within 24 hours of each other. The FBI is investigating an anti-immigrant manifesto believed to have been written by the El Paso shooter, 21-year-old Patrick Crusius. The manifesto describes the author's fear that Hispanic "invaders" would turn Texas into a "Democratic stronghold."

After the El Paso shooting, the Southern Poverty Law Center, which monitors hate groups and other extremists in the US, released a statement about the manifesto and Crusius' purported social media accounts that also contain white nationalist and anti-immigrant remarks.

The SPLC's Intelligence Project Director, Heidi Beirich, told INSIDER that manifestos and online posts containing these sentiments are "not a new phenomenon," given that the New Zealand Christchurch mosque mass shooting perpetrator who killed 51 people also issued a similar manifesto.

—Southern Poverty Law Center (@splcenter) August 4, 2019

Beirich also noted that domestic terrorism in 2018 in the US was predominantly rooted in white supremacy, including the Charlottesville, Virginia "Unite the Right" riot that resulted in the death of activist Heather Heyer. Both hate crimes and mass shootings are on the rise in the US, with the latter becoming both more numerous and more deadly.

"What we've seen is a great decline in Islamic extremist terrorism, at least within the boundaries of our country, and a rise of this kind of violence," Beirich said, noting that President Donald Trump's racist rhetoric has encouraged the phenomenon. She mentioned his recent attacks on progressive freshman congresswoman of color, in which Trump suggested they "go back" to their countries, despite three out of four being born in the US.

"What Trump has done since the day he started his campaign on that escalator in New York and talked about Mexicans as 'rapists,' is that he's emboldened white supremacists because he has legitimized their anti-immigrant, anti-Muslim, and other views," Beirich said.

Read more: Gunmen in attacks on El Paso Walmart and New Zealand mosques were tied to racist manifestos on the same website. The founder says the online community would likely be responsible for future tragedies.

Beirich pointed out that the language in the manifesto echoed Trump's own talking points, with phrases like "invading" and "infesting" used to describe Latino immigrants and asylum seekers. Her assertion is shared by 2020 Democratic presidential candidates, including Beto O'Rourk, who is from El Paso, and said Saturday that the president is encouraging attacks on immigrants.

"These are narratives that you just don't expect to hear out of the White House, you expect to hear from somebody like David Duke," Beirich said, referencing the former Grand Wizard of the Ku Klux Klan. "It legitimizes fears of Latinos. The guys' manifesto in some ways embodied the same language we've heard on Trump's Twitter feed."

Following the shooting, a clip of Trump laughing during a rally following a cry from the audience to shoot migrants at the border went viral, with users drawing parallels between the seeming call to action and the El Paso massacre.

Beirich also responded to White House Chief of Staff Mick Mulvaney's Sunday assertion that "no politician is to blame" for the weekend's mass shootings, and his call to further investigate the link between social media and mass violence. She agrees that social media plays a role in incubating white nationalist sentiments, but noted that platforms like 4chan and 8chan "are unregulated spaces whose owners don't care about this stuff at all."

—ABC News Politics (@ABCPolitics) August 4, 2019

Beirich told INSIDER that platforms like PayPal, Facebook, and YouTube have established awareness of the problem of white supremacist content and users, and are actively taking steps to combat hate speech. She says the SPLC has been lobbying big tech companies since before the Charlottesville riots, and that most major platforms besides Twitter, where Trump frequently issues racist rhetoric, have implemented changes.

"If the social media companies can start doing something about white supremacy and call it out for what it is and say that it's dangerous and it's poisoning people's minds, you'd think that Trump could do the same," Beirich said. "Mulvaney is basically dodging the issue here, which is the tech world knows this is a problem and is trying to fix it for the most part, and the President of the United States is fueling it on his own social media account on Twitter.

She told INSIDER that members of the GOP and those in high office need to condemn Trump's language, along with any racist, anti-immigrant language used by elected officials like Representative Steve King from Iowa, who was removed from his House committee seats in Janurary for defending white supremacy.

"Call it for what it is, which is either racist or anti-immigrant, and say that it has no place in polite society," Beirich said. "Trump has also said after the Christchurch shooting that white nationalism is not really a big problem, while his FBI director is saying it's the biggest domestic terrorism problem we have. That kind of conflicting messaging has to stop. Trump has to stop."

Beirich also discouraged the idea that the El Paso mass shooting was a mental health issue, noting that radicalization into white supremacy is "a reality" separate from mental illness.

"Our public officials need to accept that we have massive hate-driven violence going on and that needs to be our focus," Beirich said. "I think if Trump were to stop fanning the flames and if GOP folks who have said racist things like Steve King were stopped and other members of the party said 'We're not a party for hate, we're not gonna do this,' that would help greatly.

"But we've already got the ball rolling. We've got two years of the Trump presidency, we don't know how many young men were radicalized into white supremacy before the tech companies took this seriously. The problem is absolutely not going to go away, because we fueled it, Trump fueled it, we've got the ball rolling. Hate speech has spread everywhere [...] Every bit of what he's done has helped fuel this."

On Saturday evening, Trump tweeted "I know that I stand with everyone in this Country to condemn today's hateful act. There are no reasons or excuses that will ever justify killing innocent people." Ivanka Trump was more explicit in her condemnations, writing, "White supremacy, like all other forms of terrorism, is an evil that must be destroyed." Instead of advocating for gun control, she promoted reform around resources dedicated to mental health support.

This article has been updated to reflect the latest casualty count from both mass shootings.