What role does ideology play in mass shootings?

In their political views, the gunmen who brought carnage to two American cities last weekend could not have been more different.

One posted a lengthy screed railing against the “Hispanic invasion of Texas” and supported President Trump.

The other apparently identified as a leftist, taking to Twitter to support Democratic presidential candidate Elizabeth Warren and proclaim, “Kill every fascist.”

As the nation struggles to understand the motives behind the attacks, political ideology has become a focus.

Prominent Democrats have accused Trump of emboldening white nationalists with his divisive rhetoric on race, noting that his trope of an immigrant “invasion” was echoed in the manifesto written by 21-year-old Patrick Crusius before he opened fire in an El Paso Walmart, killing 22 people.

“We have a president right now who traffics in this hatred, who incites this violence, who calls Mexican immigrants rapists and criminals, calls asylum seekers animals and an infestation,” Beto O’Rourke, the Democratic presidential candidate who represented El Paso in Congress, said Sunday at a vigil.

Trump countered that his critics were purposely ignoring left-wing views of Connor Betts, the 24-year-old who killed nine people in a crowded bar in Dayton, Ohio.

“In Dayton, it just came out ... he was a fan of Bernie Sanders and Elizabeth Warren — nothing to do with Trump, but nobody ever mentions that,” he said Wednesday at the White House before spending the day visiting both cities. “I don’t blame Elizabeth Warren, I don’t blame Bernie Sanders, in the case of Ohio — I don’t blame anybody. These are sick people. These are really people who are mentally ill — who are disturbed.”

That position has been a talking point for the president’s defenders.

“When the media found out that the Dayton, Ohio, shooter was a Bernie Sanders socialist supporter they were absolutely silent,” Hunter Pollack, brother of Parkland, Fla., shooting victim Meadow Pollack, said Tuesday on Fox News. “The hypocrisy they show is absolutely vile.”

Experts who study mass shootings say many factors must be considered when trying to determine a motive. Though political views generally play less of a role than personal problems and dysfunction, the publicly available evidence suggests that political ideology played a role in El Paso but not in Dayton.

One important question is whether the choice of target lines up with the perpetrator’s stated ideology, said Adam Lankford, a professor of criminology at the University of Alabama.

“That seems to hold true a little bit more with the El Paso shooter at first view than it does with the Dayton shooter,” he said.

Crusius drove more than 600 miles to carry out his attack in a predominantly Latino community — a central reason that law enforcement officials believe he was motivated by the political views in the 2,300-word manifesto posted on the website 8chan.

“I am simply defending my country from cultural and ethnic replacement brought on by an invasion,” it said.

In contrast, officials have not determined the motive of the Ohio killer or whether his political views played a role. The bar had a racially diverse clientele, and the dead included his sister and apparently random bystanders.

Ernesto Verdeja, an assistant professor of political science and peace studies at the University of Notre Dame, said the shooting in El Paso was a “political terror attack” but the Dayton shooting was not. He said attempts to cast both as being equally motivated by politics were disingenuous.

“There’s a kind of a false equivalence — that one killer is on the right, another killer is on the left, and that the problem is really hateful, divisive discourse from across the political spectrum,” Verdeja said.

“But we’re not seeing the same kind of discourse on the two political sides right now,” he added. “With President Trump, there is a consistent use of dismissive, hateful, racist language that creates conditions that encourage or at least sanction the use of violence. Elizabeth Warren and Bernie Sanders simply don’t do that.”

At the same time, mass-shooting experts say the attention on political ideology this week has obscured the fact that family conflicts, mental health problems, suicidal feelings or failure at work or school tend to be more important than political views in motivating killers.

“Personal struggles are far more significant as the driving force than political ones for these individuals,” Lankford said.

“Often, mass shooters perceive themselves to be victims or to have been hurt in some way,” he said. “They need to create a narrative that leverages their feeling of pain and then justifies violence as self-defense. Rather than having to create their own story, they can just latch on to the ideology.”

For that reason, Lankford was wary of drawing a direct link between Donald Trump and the El Paso gunman.

“Can we say definitively that this mass shooting would not have happened under a different president?” he said. “I’m not comfortable saying that, because it’s possible the perpetrator would have found a different justification for his shooting.”

Crusius is not the first mass shooter to invoke Trump’s rhetoric. Those who have said they were inspired by the president’s words include James Fields, a white nationalist who killed a protester with his car in Charlottesville, and Cesar Sayoc, who was sentenced to 20 years in prison this week for mailing pipe bombs to Trump critics and media.

Prosecutors in El Paso have charged Crusius with capital murder. Federal authorities say they are separately pursuing a domestic terrorism case and considering hate crime charges.

The Dayton shooter did not leave a manifesto, but a Twitter bio believed to be associated with him, @iamthespookster, reads: “he/him / anime fan / metalhead / leftist / I’m going to hell and I’m not coming back.”

On the day of the shooting, he retweeted a post saying, “Millenials have a message for the Joe Biden generation: hurry up and die.”

Two months earlier, he wrote: “I want socialism, and i’ll not wait for the idiots to finally come round to understanding.”