Image copyright Getty Images Image caption People run from the Route 91 Country Music Festival in Las Vegas after shooting begins

Mass shootings in the United States are a depressingly familiar occurrence. But why do conspiracy theories spring up and spread so rapidly online in the aftermath of such horrific events?

There is a mass shooting in the US an average of once a day, according to data compiled by the Gun Violence Archive.

After each big shooting, a familiar script follows. Thoughts and prayers are proffered. #PrayFor(InsertLatestTownHere) trends on Twitter. Rival politicians argue about when the best time to talk about gun control might be. And then most of the world seems to move on and forget about it, until the next one.

To that script, a disturbing and relatively new phenomenon has been added. Victims are increasingly forced to fend off allegations that the shooting never happened, fuelled by conspiracy theorists on social media.

Among keyboard mourning and 280-character fury, a small but determined minority spring up in the wake of mass shootings to insist that events were staged - concocting monstrously complex tales involving "crisis actors", the "deep state" and accusations that attacks are "false flag" murders being used, for example, as a pretext to institute gun control reforms.

'Have some respect'

On 1 October 2017, Stephen Paddock took position in a Las Vegas hotel room and opened fire. Police say he acted alone. His motives remain unclear, but he killed 58 people and injured hundreds more before he was found dead in his room from a self-inflicted gunshot wound.

It was the deadliest mass shooting in modern US history. And within a day, survivors were already getting hounded on social media.

"Let me explain something for people who clearly don't get it," wrote one, Crystal Huber, on Facebook. "Just stop already with the conspiracy ideas... have some respect for people who experienced this in real life and not just in social media!" she wrote.

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But the conspiracy theorists were just getting started. Alex Jones of Infowars was claiming the facts behind the mass slaughter were being made up or covered up. His baseless evaluation claimed that so-called Islamic State, the CIA, the FBI and the government of Saudi Arabia were co-ordinating events.

"Vegas is as phony as a three dollar bill or as Obama's birth certificate" he told a caller to his show in November, pushing one conspiracy theory by referencing another: the thoroughly debunked claim that former president Barack Obama was not born in the United States. The current president, Donald Trump, was one of the most prominent voices pushing the "birther" conspiracy, until he publicly recanted during the 2016 election campaign.

Jones has form. He was also a leading pusher of the conspiracy theory that a mass shooting at a primary school in Sandy Hook, Connecticut, was made up.

But it's not only in Jones' evidentiary vacuum where one will find Vegas conspiracy theories being pushed. In darker corners of Reddit, Twitter, Facebook and YouTube, amateur sleuths congregate, eyewitness testimony is pored over and endless video "proofs" with names like "Las Vegas Shooting - an Illuminati masterminded agenda" are shared.

Does it matter?

The Guardian reports that one survivor, Braden Matejka, has been forced off social media by the reams of abuse and harassment he's faced in the aftermath - a victim forced to relive a moment of trauma over and over again thanks to people who claim that moment never happened and that he is an actor employed as the public face of a shady government plot.

Conspiracy theories around mass shootings have had real life consequences. Parents of children murdered at Sandy Hook have received death threats from conspiracy theorists.

David Neiwert, the author of Alt-America: The rise of the radical right in the age of Trump, believes that conspiracy theories are a key component of the online radicalisation process, and that they can even lead to more murders and more mass shootings.

Image copyright Getty Images Image caption Dylann Roof murdered nine African American churchgoers in Charleston in 2015

"The person who most embodies this process on the alt right is Dylann Roof, the young man who walked into that black church in June of 2015 and murdered nine people," Neiwert says.

"He was almost entirely radicalised online. He had been reading these racist websites - chatting with people on Stormfront - and doing these things that are pretty much a typical arc that we've seen for people who are drawn into these movements.

"One of the real keys to the personality types we've seen involved in these acts of extreme violence is that they are believers in conspiracy theories.

"They're wrapped up in all of these various conspiracies."

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In Roof's "manifesto" - an incoherent, racist vision of white racial superiority - he documents his own radicalisation.

In 2012, the unarmed 17-year-old African American teenager Trayvon Martin was shot dead by George Zimmerman, a neighbourhood watch volunteer. In 2013, a jury ruled that Zimmerman had acted in self defence. His acquittal sparked massive protests across the US.

"It was obvious that Zimmerman was in the right," Roof wrote. "But more importantly this prompted me to type in the words 'black on white crime' into Google.

"From this point I researched deeper."

Roof went on to immerse himself in racist conspiracy theories and false statistics he found on white supremacist websites.

Alt-America

Neiwert sees two worlds existing independently in modern America - one inhabited by the mainstream media and most of the population - and another, which he terms "Alt-America", which exists below the surface.

"'Alt-America' describes this epistemological bubble that the radical right for decades has built itself around," he says.

"In this worldview, everything is upside down. Barack Obama is a secret Muslim. There is a nefarious plot by the globalist New World Order to enslave all of mankind and to put us in federally run concentration camps.

"The alt-right is very much a subset of the radical right generally. But they're a newer phenomenon and they're almost entirely fuelled online.

"They had this whole theory that actually originated with white nationalists back in the 1990s called 'cultural Marxism'... part of a large nefarious plot to destroy white Western civilisation and drive it down."

Image copyright Getty Images Image caption An Aryan Nations member with racist tattoos during the Aryan World Congress in 2004 in Idaho

Neiwert is worried. A journalist and, since 2013, correspondent for the Southern Poverty Law Centre, he's been documenting and investigating the activities of the far right for much of his adult life. He cut his teeth writing about the white supremacist Aryan Nations group in 1970s Idaho.

"These movements are profoundly anti-democratic," he says. "They are hostile to democracy in every way and they are quite explicit about it.

"In a lot of ways what we're experiencing is this floodtide of authoritarianism. Not just in the United States, but around the world. It's happening in Europe too.

"What happens when you get drawn into this world of conspiracy theories is that dehumanisation becomes really simple. Suddenly these are no longer human beings you are talking about - they're nefarious plotters or hapless pawns in the nefarious plots.

"In the really classic example of that is the people who believe that the Sandy Hook school shooting was a hoax and that those children never really existed. So they actually go and plague the parents of those children and accuse them of being part of this plot, tell them that their child never really existed.

"That is what happens when people fall down into that rabbit hole of these conspiracy theories and a lot of the time they never come out."

Blog by Chris Bell

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