Twitter, Facebook and Instagram have been flooded with more attacks against the pizzeria as believers in the child-trafficking conspiracy became more zealous. Within hours of the publication of one of the debunking articles, a post on Twitter by Representative Steven Smith of the 15th District of Georgia — not a real lawmaker and not a real district — warned that what was fake was the information being peddled by the mainstream media. It was retweeted dozens of times.
On YouTube, a step-by-step takedown of the Times article was viewed nearly 250,000 times and passed around on Twitter and Facebook. A surge of new fake articles amplified the original pieces, now linking the child-abuse ring — known as Pizzagate — to a global pedophilia ring reaching Britain.
“We should all condemn the efforts of certain people to spread malicious and utterly false accusations about Comet Ping Pong,” James Alefantis, the owner of Comet Ping Pong, said in a statement on Sunday. Mr. Alefantis, who has repeatedly refuted the fake news articles, has closed the pizzeria for a few days. He has prominent Democratic friends and previously communicated with Mrs. Clinton’s campaign chairman, which he has said may have made him a target.
The shooting underscores the stubborn lasting power of fake news and how hard it is to stamp out. Debunking false news articles can sometimes stoke the outrage of the believers, leading fake news purveyors to feed that appetite with more misinformation. Efforts by social media companies to control the spread of these stories are limited, and shutting one online discussion thread down simply pushes the fake news creators to move to another space online.
“The reason why it’s so hard to stop fake news is that the facts don’t change people’s minds,” said Leslie Harris, a former president of the Center for Democracy & Technology, a nonprofit that promotes free speech and open internet policies. When users are caught abusing the terms of one media platform, they simply go to another, she said.
The viral nature of the misinformation was illustrated again late Sunday, not long after the police arrested Mr. Welch and called Pizzagate a “fictitious online conspiracy theory” in their report. Some individuals on Twitter said Mr. Welch was an actor used by the mainstream media to divert attention from the alleged crimes at Comet Ping Pong. Followers of a shuttered Reddit thread on Pizzagate dissected the episode on a new online network called Voat.
The storm of fake news has swept up not only Comet Ping Pong, but its neighboring businesses. Conspiracy theorists have linked symbols that some local businesses on the same street as Comet Ping Pong used in their logos to symbols of pedophilia code.
At Terasol, a French restaurant across the street from Comet Ping Pong, the owner, Sabrina Ousmaal, said she received daily phone threats and her business’s Facebook page had been filled with false accusations, including, “You guys mind explaining the pedophilia symbol removed from your website then?” She added that the symbol was not on her restaurant but on the store of a nearby shop and was a swirl within a triangle.
Ms. Ousmaal said she and her husband had called the police and the F.B.I. but had received little guidance. “I am appalled and horrified,” Ms. Ousmaal said of the shooting on Sunday. “Nothing has been done. This is not free speech. This is a hate crime.”
Tech companies and government leaders have been struggling to solve the problem of fake news, with Facebook’s chief executive, Mark Zuckerberg, earlier promising to work on technology tools to slow the gusher of false digital information. In a news briefing on Monday, Josh Earnest, the White House press secretary, said free speech rights pose a challenge for media platforms to prevent misinformation from leading to episodes like the gunman at Comet Ping Pong.
“Many of the entrepreneurs in Silicon Valley didn’t develop this technology to make it easier for hate to be propagated online; their idea was to build a community where people could more effectively communicate and engage in commerce,” Mr. Earnest said. “If you do administer a platform that is used extensively to propagate hate and to inspire acts of violence, well, I think most people are going to be less likely to use the platform.”
For purveyors of fake news who have continued pushing the Pizzagate theory even after the facts have been debunked, whether Comet Ping Pong is even engaged in a pedophilia ring is beyond the point. Jeffrey Marty, a lawyer from Florida, said in a phone interview that he was the man posing as Representative Steven Smith from Georgia’s fictional 15th District. He said that he was frustrated with the way the mainstream media covered the election and that he believes that most of his 24,000 followers know that his account is a parody.
Mr. Marty, who has tweeted links to fake news stories and repeatedly said the mainstream media needs to investigate Pizzagate, declined to say whether he actually believed the Comet Ping Pong allegations. “I just think you need to investigate. There are clues everywhere,” he said. “But I don’t agree with what happened at the restaurant.”
Mr. Welch has long supported family values, his friends said Monday. He briefly volunteered at the Locke Township Fire Department in Salisbury, according to the chief, Rusty Alexander. Friends described Mr. Welch as a doting father who loved the outdoors. While he had been arrested while driving impaired in 2013 and was sentenced to probation, the shooting on Sunday was out of character, his friends said.
“That’s not at all the person I know,” Louis Bodak, whose son Matthew is a good friend of Mr. Welch’s, said about the shooting.
Mr. Welch is scheduled to appear in court again on Thursday.
An earlier version of this article misspelled the given name of the Florida lawyer posing as Representative Steven Smith, the fictitious congressman from Georgia. He is Jeffrey Marty, not Jeffery.