“You rape our women and you're taking over our country. And you have to go.” With those words, witnesses report, Dylann Storm Roof opened fire on the congregants gathered for a Bible study at the historic Emanuel AME church in Charleston, South Carolina, Wednesday night. Nine people died, all African-American. Roof, 21, is white.

That Roof’s alleged crimes stem from deep reserves of hate is clear enough. But, as a recently unearthed manifesto likely written by Roof reveals, they draw on a set of racial myths that have proved remarkably persistent in American culture.

Roof’s alleged writings repeat centuries-old narratives, such as African-American intellectual inferiority and white victimhood, that continue to manifest in venues ranging from fringe hate groups to mainstream media.

Though his ramblings could be written off as “insane” or “demented” -- and while some mainstream news outlets have appeared perplexed at Roof’s motives -- research shows the misconceptions Roof cited as justification for racist mass murder are deeply ingrained in the popular imagination.

'I Was In Disbelief'

The manifesto identifies a moment of awakening: the killing of Trayvon Martin, 17, an African-American whose death at the hands of self-appointed neighborhood watch George Zimmerman sparked national outrage.

“[T]his prompted me to type in the words ‘black on White crime’ into Google, and I have never been the same since that day. ... How could the news be blowing up the Trayvon Martin case while hundreds of these black on White murders got ignored?”

Indeed, search results for “black-on-white crime” reveal numerous sites, many of which obsess over lurid anecdotes of grisly interracial crimes.

“The first website I came to was the Council of Conservative Citizens,” Roof allegedly writes, referring to a neoconfederate group founded in 1985. “There were pages upon pages of these brutal black on White murders. I was in disbelief.”

Statistics, however, belie the perception white people are particularly at risk of black crime. According to the most recent FBI crime data, African-American offenders were identified in 13.6 percent of homicides where the victim was white. African-Americans make up 13 to 15 percent of the overall population, depending on how mixed-race individuals identify.

The myth’s endurance, however, isn’t explained only by the power of hate groups -- which have exploded in number since 2009. A diverse array of research has found mainstream media reports tend to overemphasize the prevalence of black-on-white crime, creating a jaundiced view of black criminality.

As a report from the Sentencing Project outlined in 2014, local media had a tendency “to exaggerate rates of black offending and white victimization and to depict black suspects in a less favorable light than whites.”

Capitalizing on the perceived novelty of black-on-white crime, news outlets have been found to air more images of black suspects -- and of white victims -- than really occur. One study found 37 percent of perpetrators shown on Los Angeles television stations were black, while only 21 percent of those arrested were black. Another study found nationwide, local news stations overreported the prevalence of black-on-white homicide by a factor of four.

Though these patterns are hard to see on a case-by-case basis, their effects are clear. In surveys, white Americans steeply exaggerate the risks of minority perpetrators. A 1994 study found whites were twice as likely to believe themselves at risk of being harmed by minorities even though they are three times as likely to be victimized by other whites.

'Our Women'

Though Roof’s purported manifesto contains no mention of rape, his chilling words reported on the night of the mass murder reveal a preoccupation with sexual violence against white women.

White perceptions of black men as sexual predators have a long, sordid history. Of the thousands of black men lynched in the late 19th and early 20th centuries, many stood accused of making passes at white women. In 1916, for instance, Jeff Brown of Cedarbluff, Mississippi, brushed against a white woman while racing to make a train. He was dragged from the moving locomotive, beaten and hanged. Photos of his lynching sold for a nickel.

Fascination with black-on-white rape has been kept alive by media representations, from Cecil B. DeMille’s 1915 film Birth of a Nation -- which depicted a white woman escaping the clutches of an actor in black-face by throwing herself off a cliff -- to the 1989 Central Park jogger case, in which local news rushed to portray five African-American juveniles as monstrous perpetrators in the rape of a jogger in Central Park. They spent a combined four decades in prison before it was determined they were innocent.

In reality, Americans are far more likely to be raped by members of their own racial group. According to the Department of Justice, 88 percent of all rape victims were attacked by members of their own race. A full two-thirds of rapes occur between people who know each other well.

In fact, on the aggregate, African-American women are more likely to be targeted than white women.

Inside And Outside

In Roof’s alleged writings, the author makes claims about intelligence he finds to be self-evident: “Anyone who thinks that White and black people look as different as we do on the outside, but are somehow magically the same on the inside, is delusional. How could our faces, skin, hair, and body structure all be different, but our brains be exactly the same?”

These biases, too, have a long history, from the creation of racial categories through the eugenicist foundation of intelligence testing to bestselling books in the modern era.

The book "The Bell Curve," for instance, set off an explosive public debate in the 1990s, arguing genetic differences in intelligence existed between races, as evidenced by IQ test results. Even today, co-author Charles Murray remains a fixture in mainstream intellectual circles.

The overwhelming majority of scientists in the field dispute the theory of racial differences in intelligence. Two of the major difficulties finding any correlation whatsoever between race and intelligence are the facts there is no biologically sound definition of race and no error-free way of measuring intelligence.

As evolutionary biologist Richard Sternberg wrote in 2005, “Race is a social construction, not a biological construct, and studies currently indicating alleged genetic bases of racial differences in intelligence fail to make their point even for these social-defined groups.”

The differences that do exist between African-Americans and whites on intelligence tests can be largely explained by socioeconomic factors. Being raised in a well-off family raises IQ scores by 12 to 16 points, a French study found. While children of different parents might have differing innate abilities, the impact of social and environmental factors far outstrips these slight variations.

'A Lot Of Racist Jokes'

A fuller picture of Roof’s thinking and motives will undoubtedly emerge in the months and years to come. But a growing number of reports show that while Roof expressed views that the vast majority of Americans would find repugnant, they didn’t necessarily raise alarms among those who knew him.

As one friend told the Daily Beast: “He made a lot of racist jokes, but you don’t really take them seriously like that. You don’t really think of it like that.”

As Charleston comes to grips with the tragic deaths of nine community members, Roof’s convictions will be taken increasingly seriously. Faulty and biased as they may be, they reflect beliefs as persistent and visible as the Confederate flag that still flies above the Charleston courthouse.