The disappearances and deaths of at least 10 people tied to sensitive US research have drawn scrutiny from online sleuths and now federal investigators. But for grieving relatives, all the wild speculation is "disgusting".

Carl Grillmair "would laugh" at the conspiracy theories about his killing, says his widow.

"I think it's absolute nonsense," says Louise Grillmair. "I mean, there's the facts, and they're out there."

Her 67-year-old husband was gunned down at their Llano, California, home in February.

Grillmair's alleged killer, a 29-year-old local man, Freddy Snyder, has been charged with murder and burglary and is due in court next week for his arraignment.

Despite the arrest, Grillmair figures prominently in conspiracy theories about the deaths and disappearances of about 10 people with connections to top-secret labs or scientific work.

They are often lumped together as "missing scientists", but the list includes an administrative assistant, an Air Force general, an engineer and a custodian, and spans several fields, from researching exoplanets to pharmaceuticals.

Online sleuths have suggested the cases may be connected, even prompting the US House of Representatives Oversight Committee and the FBI to announce investigations - despite other established explanations and family members' attempts to quell the hysteria.

Grillmair's wife believes her husband was targeted in a misguided revenge plot.

Months before the killing, a man had "wandered on [their property] with a rifle", claiming to be coyote hunting. She says her husband directed the suspect to a nearby ridge.

The man had also been causing mischief at other homes nearby, she says, and one resident called 911. Grillmair hadn't placed the call, but his wife believes the man blamed her husband for it as his behaviour was "escalating".

The man came back with a baseball bat two weeks before Grillmair was killed, but left without causing anymore trouble that day, she said.

Then he returned on 16 February and allegedly fatally shot Grillmair, a renowned astronomer at the California Institute of Technology's IPAC science and data centre for astronomy and planetary science.

"We believe [he] came for revenge, thinking Carl was the one that called 911," says Louise.

She says her late husband was "probably the nicest guy that walked the face of the Earth".

Sceptics have poured cold water on the wild theories surrounding the deaths.

"The US Top Secret-cleared aerospace and nuclear workforce is ~700,000 people," science writer, investigator and pseudoscience debunker Mick West wrote on 16 April on his Substack.

"Ordinary mortality over 22 months predicts ~4,000 deaths, ~70 homicides, and ~180 suicides. The list has 10 … The deaths are real. The families' grief is real. The pattern is not."

Louise Grillmair, similarly, says that - while her husband "would laugh" at speculation that the deaths might be connected - he would also "probably talk statistically" to squelch conspiracies.

The wife of retired Air Force General William Neil McCasland - the highest-ranking and highest-profile of the missing - took to Facebook the week after his 27 February disappearance from their New Mexico home to "dispel some of the misinformation circulating".

She told the dispatcher that he'd turned off his phone and left it behind, but took his gun, though he "doesn't generally" carry a weapon.

She also noted that her husband had recently been suffering from anxiety, short-term memory loss and lack of sleep - and he'd been "saying if his brain and body keep deteriorating, he doesn't want to live like that".

On Facebook one week later, she wrote that, while McCasland had access during his Air Force career to "some highly classified programs and information", he had retired "almost 13 years ago and has had only very commonly held clearances since. It seems quite unlikely that he was taken to extract very dated secrets from him."

She also acknowledged that McCasland had acted as an unpaid consultant for Blink-182 frontman Tom DeLonge's To The Stars organisation as it sought to investigate UFOs and other matters.

But her husband "does not have any special knowledge about the ET bodies and debris from the Roswell crash stored at Wright-Patt," Susan wrote.

She was referring to Wright-Patterson Air Force Base in Ohio, which UFO lore speculates might be the final resting place of extraterrestrial remains from unusual debris found by a rancher in Roswell, New Mexico, in 1947.

Drily addressing the conspiracy theories, Susan wrote: "At this point with absolutely no sign of him, maybe the best hypothesis is that aliens beamed him up to the mothership.

"However, no sightings of a mothership hovering above the Sandia Mountains have been reported."

Eight months before McCasland's disappearance, also in New Mexico but 135 miles (220km) away in Taos, an administrative assistant at Los Alamos National Laboratory vanished.

The family of Melissa Casias also addressed the case on Facebook - again indicating that their loved one left deliberately. Their comments did little to dampen theorists' obsession with her case.

"It's been the hardest six weeks of our life with out you," her husband, Mark Casias, wrote on Facebook in August 2025.

"Sierra and I are starting to worry more every day about you, we believe you are ok but can't understand why you haven't reached out.

MIT physicist Nuno Loureiro was murdered by a former classmate who was also arrested for additional killings at Brown University - and the suspect confessed on video recordings later discovered by authorities.

Another researcher vanished from his home the month after losing both parents within hours of each other, his father suffering a fatal heart in his arms right after his mother's death.

His body was later found in a lake, and his wife told US media how bereft her husband - an only child - had been following his parents' death.

Another scientist died of "arteriosclerotic cardiovascular disease" at the age of 59, according to a 2023 coroner's report.

Louise Grillmair says the explanations appeared to be no deterrent for conspiracy theorists - she's even "been contacted by many of them" asking her opinion.

"I said, 'Well, I can do better than an opinion,'" she says. "I have the facts."

The speculation, she says, is "denigrating to their memories".

Other loved ones reached by the BBC called the speculation "terrible" and "disgusting," compounding families' grief - but chose not to speak on the record because they didn't want to give the stories any more airtime.

For Louise Grillmair, who met her husband in an astrophysics class, she would prefer that the world know not just about his groundbreaking scientific work, but also his kind and generous character.

"He helped everyone who needed help," she says. "For example, he got into two quite serious car accidents… and he didn't believe in suing. I mean, it was the other guys' fault, and he just wouldn't sue."

His obituary remembered Grillmair as "an avid pilot, flying small aircraft and gliders that he owned and maintained at his home; he would cheerfully accept requests to fly with him".

"Friends and associates recall that he loved the outdoors, driving tractors, and doing repairs and other construction work on his house, where he also kept a small observatory with several telescopes." (BBC, excluding headline)

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