In early October 2017, a rumor surfaced online alleging that a person using only the name "john" on the messaging board 4chan had "predicted" the mass shooting in Las Vegas on 1 October 2017.
Police say a 64-year-old gunman opened fire from the 32nd floor of the Mandalay Bay Resort and Casino on a crowd of 22,000 people gathered below for the Route 91 Harvest Festival at 10:05 p.m. on 1 October. The attacker had modified a semi-automatic firearm so that it fired like an automatic, and for roughly ten minutes he sprayed the concert crowd with bullets, killing 58 people and wounding hundreds.
As with many mass casualty incidents in recent history, conspiracy theorists immediately pounced, claiming without proof, for example, that there was a second gunman on the fourth floor of the hotel or that internet sleuths had spotted footage of the shooter at an anti-Trump rally. In keeping with this pattern, conspiracy-minded web sites Neon Nettle and WorldTruth.tv posted identical stories claiming that an anonymous 4chan user predicted the Las Vegas Strip massacre three weeks before it occurred. NeonNettle reported:
The ominous warning was left on the anonymous message boards on the 16th anniversary of the 9/11 attacks. The user warned people to "stay away" from Las Vegas due to a coming deadly attack. The mysterious 4chan user, who went only by the name "John", made a series of, at the time, overlooked posts. He warned other users to avoid gatherings of large groups of people in the Vegas or nearby Henderson areas. John claimed to have inside knowledge of, what he referred to as, a "high incident project" that was due to take place soon.
The messages posted by "John" on either 10 September or 11 September 2017 (depending where you look) don't in fact predict any specific catastrophe -- he only said vaguely that some kind of incident would occur the following day in Las Vegas or Henderson, and that a harbinger of this disaster will be "three black vans parked next to either."
According an alleged screen shot and archive of his comments, reposted to 4chan the day after the shooting (with the thread title, "Anon 'jon' predicted Vegas attack") the anonymous user issued the warning a day before the 16th anniversary of the 11 September terrorist attack, which could point to a troll trying to drum up fear as the anniversary approached. The user wrote:
look i feel bad for some of you on this website. so i'll let you in on a little secret. if you live in las vegas or henderson stay inside tomorrow. don't go anywhere where there are large groups of people. also if you see three blacks vans parked next to each other immediately leave the area. you're welcome
-john[...]
it's called the "high incident project". they want to make the american public think that places with extremely high security aren't safe. they are trying to create more regulations. you will see laws proposed within the next few years to put up more metal detectors and other security devices. media and politicians will be saying places with lots of police need even more police. i can't guarantee anything will happen tomorrow but las vegas is on their minds.
-john[...]
if their plan is successful state of nevada will pass a law in the future making all casinos have mandatory metal detectors and backscatter machines. soon after a federal law will be passed to put these machines in universities, high schools, federal buildings, you name it. osi systems and chertoff are the main producers of these machines. sometime around 2020 chertoff and osi will merge into a single company. after they merge the owners will sell off all their stock and make billions in profit. mr chertoff has been in contact with sheldon adelson. mr adelson will become a huge sponsor of these machines and he will be the first to put them in his casinos when the law passes. this is my last message for now. don't expect me to return anytime soon
-john
Although some 4chan users questioned whether the person who wrote the posts was the Las Vegas gunman, others didn't seem impressed at all, saying the user had a habit of regularly posting vague predictions. As one person pointed out, "Make 1000 predictions a year and a couple will come true." Another 4chan user noted that the name "john" may reference John Titor, a message board hoax from the early 2000s that depicted a time traveling soldier from the future who made bogus predictions about catastrophic events.
We don't know who posted these messages, nor do we know whether the person who did so posts similar messages regularly. They gave the wrong date and didn't refer to any specifics that would point to knowledge predicting the Strip attack. The aspect of the prediction that was correct was the location, but even that was general. Predictably both Neon Nettle and WorldTruth.tv used the posts to support the claim that the attack was a "false flag" -- a prevailing conspiracy theory that posits mass casualty incidents are engineered by the government to serve as pretense for heightened security and surveillance, and/or tighter gun control legislation.