They originate in the dark corners of the internet -- often from the 4chan "politically incorrect" board (abbreviated as /pol/) -- and migrate onto social media platforms like Twitter, YouTube and Facebook from conservative pages, alt-right personalities, nationalist blogs and far-right pundits.
What drives hoaxes and conspiracy theorists is unclear. But their faith in the conspiracies they spread seems to be unwavering.
Less than an hour after the shooting at Marjory Stoneman Douglas High School in Parkland on February 14, Twitter accounts were claiming that eyewitnesses were "crisis actors." The term refers to people who are paid to play disaster victims in emergency drills. More recently, though, the phrase has been co-opted by conspiracy theorists who claim mass shootings are events staged to achieve a political goal.
A CNN investigation into 4chan's /pol/ archive counted at least 121 times that school shooting survivor David Hogg was mentioned on the board.
Conspiracy theorists appear to be focusing on Hogg and his fellow students because they have been so outspoken about gun safety issues since the shooting.
Some claim Hogg and his classmates are simply too skilled as public speakers not to be paid actors.
One such post included a link to a mugshot of another person named David Hogg, falsely claiming he'd played a role as a "crisis actor" during the shooting.
Meanwhile, a viral tweet from a now-suspended Twitter account, @LagBeachAntifa9, falsely claimed Hogg attended Redondo Shores High School in California, and that he graduated in 2015. The post itself quickly spread on 4chan's /pol/ board. "David Hogg Exposed! 2015 Year Book released: ITS HAPPENING," read one of the posts.
A location for the account claims its geotag is a city in Russia, but CNN cannot verify that.
CNN reached out to 4chan for comment twice about these false posts about Hogg, but has not yet received a response.
Someone also went as far as to create a fake, now deleted, Classmates.com profile for David Hogg, complete with picture. The since-deleted profile's source code shows the page was created on February 20, six days after the shooting.
In a statement posted to its Twitter account, Classmates.com said it was "upset to find fake accounts" and would continue to "actively monitor the situation and take further action as necessary."
How theories are repackaged and rebroadcast
Some Stoneman Douglas High School students eventually debunked the Classmates.com hoax on their personal pages. One of Hogg's classmates even created a video showing Hogg pictured in the school's 2017 yearbook.
But the original Classmates.com hoax tweet got more than 3,000 retweets and likes.
In a blog post from June 2017, Twitter said its platform was not responsible for being the "arbiters of truth."
"Open and real-time nature is a powerful antidote to the spreading of all types of false information," it read. "Journalists, experts and engaged citizens tweet side-by-side correcting and challenging public discourse in seconds."
Journalists, experts and engaged citizens weren't fast enough to keep up with the conspiracy theorists, even with the @LagBeachAntifa9's suspension.
A screenshot of the faked Classmates.com profile has over 3,000 likes on Instagram. It spread to Facebook, with one such posts reaching 111,000 shares before it was deleted, according to screenshots obtained by NBC News.
Sometimes, hoaxes like the Classmates.com profile are repackaged with other false theories.
On Wednesday, the top-trending video on YouTube captioned Hogg as an "actor," taking out of context CNN affiliate KCBS' interview with Hogg in August 2017. Hogg had witnessed a confrontation between a lifeguard and bodysurfer in Redondo Beach, California, where he was on vacation.
The caption on the video called him an "actor." Although the video was taken down by YouTube for violating its policies on bullying and harassment, the false claim simply added fuel to the fire.
One video posted by the Facebook page "Survive Our Collapse," which contained the KCBS clip among others, had more than 2 million views before it was removed by Facebook. It has since then been repackaged and uploaded again on the same page, despite a number of removals.
CNN asked Facebook if the platform has a policy relating to hoaxes and misinformation from conspiracy theories content and whether Facebook disciplines accounts that violate it.
The company directed CNN to its community standards, which state that there are consequences for violating them, and the punishment depends, "on the severity of the violation and the person's history on Facebook." It's unclear what community guideline policy Survive Our Collapse violated, and Facebook did not say what it did violate.
"One post would not result in unpublishing a page," Facebook representative Ruchika Budhraja said in an email. "Repeat violations, however, will."
However, after four inquiries, Facebook would not discuss what factors go into deciding the severity of the violation, who at Facebook decides the severity, or the internal mechanisms for determining a punishment.
Responding to the video on the Survive Our Collapse page that claimed Hogg was a crisis actor, Facebook's head of content policy Mary deBree called images attacking the victims "abhorrent" and said the content was being removed from Facebook.
CNN sent Facebook a second post from the Survive Our Collapse page that asked users to confirm the Classmates.com hoax, which implies Hogg is a crisis actor. It's still on the social media platform, where 505 people have shared it.
Websites magnify conspiracies
Hoaxes and conspiracy theories fully mature once the conspiracy establishment finds and publishes them.
InfoWars founder Alex Jones is known for spreading the conspiracy that the Sandy Hook Elementary School shooting in Newtown, Connecticut, in 2012 was fake. Of Parkland, he acknowledges that "real people were shot." But Jones still insists Hogg and others are crisis actors. He also called the Florida shooting a potential "false flag" in a February 15 video posted on YouTube.
Conspiracy believers think false flags are government operations that seek to divert or steer public discussion and policy.
has repeatedly shown its 2.2 million YouTube subscribers screenshots of the KCBS video in combination with other images in an attempt to show that Hogg and other students are "crisis actors."
Another video shows Hogg stumbling over his words in a pretaped CNN interview.
The Gateway Pundit, a far-right site with White House press credentials, suggested he stumbled because he'd "been coached on anti-Trump lines." The Gateway Pundit post about it has been shared on Facebook more than 23,600 times.
The Gateway Pundit claims that because Hogg's father is a retired FBI agent, the FBI "is only looking to curb YOUR Constitutional rights and INCREASE their power. We've seen similar moves by them many times over."
Before they present their false evidence, the discussion is already framed.
"Few have seen this type of rapid media play before, and when they have it has come from well-trained political operatives and MSM commentators," the Gateway Pundit said in its description of the school shooting survivors. "Immediately, these students-turned-activists threw up some red flags."
The same is done on InfoWars, where Milo Yiannopoulos said, "There's something odd about this" in one broadcast. Unsupported and false conspiracies are then presented as evidence.
Such claims churned out by the conspiracy establishment can fester online for years. Parents who lost children in the Sandy Hook shooting in December 2012 are still harassed by hoax believers.
Social media companies do occasionally remove hoax content from their pages, but often only when the problem is brought to their attention.
On Wednesday, YouTube removed a video from InfoWars' page for violating its policies on harassment and bullying. The video was titled, "David Hogg Can't Remember His Lines In TV Interview."
"Last summer we updated the application of our harassment policy to include hoax videos that target the victims of these tragedies," said a YouTube spokesperson. "Any video flagged to us that violates this policy is reviewed and then removed."
CNN also identified three similar YouTube videos from InfoWars and asked if they also violated YouTube's policies. The YouTube spokesperson said the videos CNN sent were flagged to the policy team for review.
YouTube's community guidelines
say if an account receives more than three strikes in three months, the account will be terminated. A source with knowledge of InfoWars' account says all YouTube accounts, including InfoWars', are subject to the community guidelines.
The source goes on to tell CNN that InfoWars' YouTube account did receive a "strike" for the video that was removed on Wednesday.
The community guidelines say if the account receives one more strike in a three-month period, the account will not be able to post new content for two weeks. If the account receives two more strikes in three months, the account will be terminated.