Washington - The bizarre rumours began with a leaked email referencing Hillary Clinton and sinister interpretations of references to pizza parties.
It morphed into fake online news stories about a child sex trafficking ring run by prominent Democrats operating out of a Washington, DC, pizza joint.
On Sunday, it culminated in violence when police say a North Carolina man fired an assault rifle inside the Comet Ping Pong restaurant as he attempted to "self-investigate" the conspiracy theory known in the Twitterverse as "Pizzagate".
No one was hurt and the man was arrested.
But the shooting alarmed those from neighbouring businesses all the way to the White House about the real life dangers of fake news on the internet.
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One of those people posting on the conspiracy theory is the son of president-elect Donald Trump's proposed national security adviser.
On Monday, White House spokesperson Josh Earnest, asked about the shooting, said: "There's no denying the corrosive effect that some of these false reports have had on our political debate, and that's concerning in a political context. It's deeply troubling that some of those false reports could lead to violence."
Edgar Maddison Welch, 28 of Salisbury, North Carolina, was arrested on Sunday afternoon outside the popular eatery in an affluent neighbourhood of the nation's capital, police said.
At his initial appearance Monday in DC Superior Court, Welch was ordered held pending a hearing scheduled for Thursday. The public defender he was assigned didn't immediately respond to an email seeking comment.
Court records made public on Monday state Welch fired an AR-15 assault rifle multiple times inside the restaurant but later walked out with his hands up and unarmed, leaving his weapons inside.
He told police he had read online that “the Comet restaurant was harbouring child sex slaves and that he wanted to see for himself if they were there". He said he "was armed to help rescue them" and "surrendered peacefully when he found no evidence that underage children were being harboured in the restaurant".
Welch was charged on multiple counts, including assault with a dangerous weapon. Authorities recovered the AR-15 assault rifle and a handgun from the restaurant, court paperwork said. Police said an additional weapon was recovered from his vehicle.
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One of Welch's friends told The Washington Post she doesn't think he intended to shoot anyone.
"He most likely really believes the conspiracy theory," said Kathy Sue Holtorf, 29, who lives in California and works as a film producer. "He's a good guy with the best of intentions. He probably saw himself as more on a hero mission to save children than anything else."
The precise origins of the conspiracy theory Welch said he went to investigate are murky, though it seems to have started gaining momentum in the week before the election.
Some elements trace back to hacked emails from Clinton Chief of Staff John Podesta that were released by Wikileaks that refer to pizza parties, with online commentators speculating that "pizza party" is a code word for something more nefarious.
By November 3, Comet Ping Pong - so named because patrons can play ping pong on tables in the back of restaurant - had been pulled into the conspiracy.
"Let me state unequivocally: These stories are completely and entirely false, and there is no basis in fact to any of them. What happened today demonstrates that promoting false and reckless conspiracy theories comes with consequences," Comet's owner, James Alefantis, said in a statement on Sunday night.
At least one person who isn't ready to give up on the conspiracy theory is prominently connected to Trump's transition team.
Michael Flynn jnr is an adviser to his father, Michael Flynn, whom Trump selected to serve as national security adviser. Flynn jnr has sent numerous posts on Twitter about the Pizzagate conspiracy theories.
Flynn jnr, who has accompanied his father to presidential transition meetings inside Trump Tower and lists the presidential transition website as part of his Twitter bio, tweeted on Sunday night that, "Until #Pizzagate proven to be false, it'll remain a story."
Trump's team had no immediate response to questions about the conspiracy theory or the younger Flynn's role in the presidential transition.
Wiktoria Skrzypinska lives a few blocks from Comet. She said she had heard the rumours about Comet but was shocked to learn that somebody had become so enmeshed in the conspiracy theory to enter the restaurant with an assault rifle.
"I guess we all knew it was fake. It was so obvious I didn't even bother with it," she said.