(AP) – Speculation about links among a handful U.S. scientists who have died or disappeared in recent years was largely confined to niche online communities less than two months ago. As of Friday, the number had grown to at least 12 and was at the epicenter of U.S. government, with both the FBI and Congress investigating possible connections.

At a press gathering April 16, President Donald Trump was asked about “10 missing scientists with access to classified stuff, nuclear material, aerospace, they’ve all gone missing or turned up dead in the last couple of months” and whether he thought there were ties among them.

“Well, I hope it’s random, but we’re going to know in the next week and a half, ” Trump said.

Those speculating about the cases suggest that the individuals were targeted, perhaps by global U.S. adversaries, because of the sensitive nature of their work related to topics such as astrophysics, nuclear weapons and pharmaceuticals. But so far no evidence has been found that definitively links them or establishes coordinated foul play.

Jen Golbeck, a professor at the University of Maryland who studies conspiracy theories, said the idea of a sinister connection between tragedies involving scientists is a common trope within conspiracy theory communities.

“There are a lot of people who work for national labs and universities and government research centers and some of them will go missing or commit suicide or die,” she said. “Any year you could take a bunch of those and name them as something sinister if you wanted to.”

The path from niche online communities to the mainstream
The deaths and disappearances in question garnered suspicion from online sleuths as they occurred, but it was the disappearance of 68-year-old William “Neil” McCasland, a retired Air Force general, on Feb. 27 that fueled a wider belief that there could be a nefarious connection between these incidents, spurred in part by his high-ranking military work and connection to the UFO community.

Around this time people began pointing to other examples of scientists who had died or gone missing, ultimately going as far back as June 2022.

The Daily Mail published an article on March 22 naming five individuals and reporting that “a chilling pattern has emerged after a string of US scientists died or went missing in recent months.”

On April 15, a question about the missing or dead individuals came up at a White House press briefing and by the next day Trump said he had met with advisers and the issue was being investigated. FBI Director Kash Patel reiterated the importance of looking for connections in these cases Sunday on Fox News. The House Committee on Oversight and Government Reform is conducting its own investigation.

“That’s pretty typical for how a lot of this stuff works, is that there are these fringe online spaces, they start it, it spreads, it gets picked up by … the more conspiratorial-minded politicians who do have platforms and makes its way onto more mainstream social media and then grabs that attention,” said Golbeck.

Callie Kalny, co-director of the Center of Media Psychology and Social Influence at Northwestern University, agreed that these conspiracy theories are following a familiar pattern of starting in more niche venues before finding their way into the national conversation.

“Once it’s made it to the mainstream and once we experience this repeat exposure to it, it sort of just embeds into our minds as something that maybe we just take as fact or we just take as something that is common knowledge without ever really critically thinking well, where did this come from to begin with? And is there any validity to this?” she said.

Correlation does not imply causation
There are some parallels among the dozen or so individuals at the heart of these conspiracy theories, such as associations with Los Alamos National Laboratory and NASA’s Jet Propulsion Laboratory, and some of those named had specialized knowledge and high-level security clearances. But the list contains many reasons to doubt the claims spreading online.

In some of the cases, investigations had already been conducted, with suspects identified or charged. In others, no connections were apparent or evidence was lacking or not as convincing as it first appeared.

For example, Nuno F.G. Loureiro, a physicist and fusion scientist who was a professor at the Massachusetts Institute of Technology, is on the list. He was fatally shot on Dec. 15 by Claudio Manuel Neves Valente, who was also responsible for a mass shooting at Brown University days prior. Neves Valente took his own life. A motive has not been established, but the two men knew each other decades earlier as classmates in Portugal studying physics.

Carl Grillmair, an astrophysicist at the California Institute of Technology who discovered water on a distant planet, was fatally shot on Feb. 16, according to local reports. Authorities charged 29-year-old Freddy Snyder with Grillmair’s murder and carjacking. Snyder is being held on a multimillion-dollar bond.

Melissa Casias, then 53, went missing on June 26 in New Mexico. She worked at Los Alamos National Laboratory and while some online assumed she was a scientist there, according to her LinkedIn profile Casias actually worked as an administrative assistant.

As for McCasland, he left home without his phone, prescription glasses and wearable devices, according to the Bernalillo County Sheriff’s Office. His hiking boots, wallet and a .38 caliber revolver could not be found at the house. There is no evidence indicating foul play and he remains missing.

McCasland’s wife, Susan Wilkerson, wrote in a Facebook post on March 6 responding to online rumors that since his retirement 13 years ago, McCasland “has had only very commonly held clearances” and that “it seems quite unlikely that he was taken to extract very dated secrets from him.” She added that although he “had a brief association with the UFO community,” he does not have any privileged knowledge about aliens.

“In the face of tragedy or uncertainty, people seek patterns and explanations rather than accepting ambiguity or coincidence,” said Donnell Probst, executive director of the National Association for Media Literacy Education. “Narratives suggesting hidden connections or intentional wrongdoing can feel more satisfying than incomplete or evolving information, even without supporting evidence.”