White House probing disappearances, deaths of US scientists: 'Pretty serious stuff'

The White House says it is looking into several U.S. scientists and government employees with high-level classified clearance who’ve gone missing or died over the past couple of years. 

President Trump was asked about their mysterious disappearances Thursday, and whether the White House believes they are connected. Here’s the latest: 

Missing U.S. scientists

What they're saying:

"I hope it's random, but we're going to know in the next week and a half," Trump told reporters Thursday. "I just left a meeting on that subject. Pretty serious stuff."

"Hopefully, I don’t know, coincidence, or whatever you want to call it, some of them were very important people, and we’re going to look at it," Trump continued. 

The cases have drawn attention because of the scientists’ and employees’ access to classified nuclear and space information, but law enforcement and even other scientists say they don’t see any connection between them. 

The other side:

Avi Loeb, a physicist and professor at Harvard University, said he doesn’t believe the cases are related, because each of them have different areas of expertise.

"The common denominator of the practicing scientists is not great, and I would caution of assigning too much significance to those," Loeb said in an interview with FOX 32’s Chicago Report. "Of course each of these cases is a mystery that has to be resolved. It’s possible there was someone aiming to harm those individuals. But I don’t think it shows some evidence for a plan, just because, these people, for example, worked on unidentified anomalous phenomenon (UAP) … I would not be too concerned with this being coordinated."

Who is missing? 

Dig deeper:

According to Fox News Digital, the following government scientists or researchers have all disappeared or died in the past two years: 

Neil McCasland

Retired Air Force Maj. Gen. Neil McCasland, who held senior roles at the Pentagon and in space research and acquisition, disappeared Feb. 27. There’s been no trace of him since. His phone, prescription glasses and wearable devices were found at home, but his hiking boots, wallet and a .38‑caliber revolver were reported missing, according to the Bernalillo County Sheriff’s Office in New Mexico. 

McCasland also commanded the Phillips Research Site of the Air Force Research Laboratory at Kirtland Air Force Base in New Mexico, and the Air Force Research Laboratory at Wright-Patterson Air Force Base in Ohio, according to the Air Force.

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McCasland’s name appeared in the 2016 WikiLeaks release of emails from Hillary Clinton campaign chairman John Podesta. In those messages, it was said that McCasland worked unidentified aerial phenomena (UAP), noting that the general had previously led the Air Force Research Laboratory at Wright-Patterson Air Force Base — a facility that’s long been linked to by UFO conspiracy theorists to the alleged 1947 Roswell crash. 

"Neil does not have any special knowledge about the ET bodies and debris from the Roswell crash stored at Wright-Patt," his wife, Susan Wilkerson, wrote on Facebook shortly after his February disappearance. 

Wilkerson said her husband retired in 2013. 

"It seems quite unlikely that he was taken to extract very dated secrets from him," she said. 

Monica Jacinto Reza

Monica Jacinton Reza, a 60-year-old aerospace engineer and co-creator of a nickel-based alloy for rocket engines, disappeared June 22, 2025, while hiking with a friend in the Angeles National Forest on a well-traveled trail.

According to the Los Angeles County Sheriff’s Department, it happened around 9 a.m. 

The friend was about 30 feet ahead, and told police he turned around to check on her and she smiled and waved, indicating she was doing fine. The friend turned back to continue hiking, and when he looked back again moments later, she was gone, he told investigators. 

Reza has not been seen or heard from since. At the time of her disappearance, she was the Director of Materials Processing at NASA’s Jet Propulsion Laboratory (JPL).

Reza’s work in advanced rocket materials was funded in part by the Air Force Research Laboratory — the same organization McCasland later led — though no direct relationship between them has been publicly confirmed.

Steven Garcia

Steven Garcia, a government contractor with ties to the Kansas City National Security Campus, disappeared Aug. 28, 2025. 

The 48-year-old was last seen leaving his home in Albuquerque around 9 a.m. He was seen surveillance footage walking away on foot while carrying a handgun. He left behind his phone, wallet, keys and car, and has not been seen since, according to Albuquerque police.

The Kansas City National Security Campus produces the vast majority of non-nuclear components used in the U.S. nuclear weapons arsenal. His role reportedly gave him high-level security clearance and oversight of sensitive assets, according to Fox News. 

Authorities initially warned Garcia "may be a danger to himself," raising concerns about his mental state. But an anonymous source familiar with the case pushed back on that assessment to media outlets, describing him as "a very stable person" and disputing suggestions that he was suicidal or experiencing mental health issues. 

Both Garcia and McCasland lived in the same part of New Mexico. The area is a hub for U.S. nuclear and defense research, though authorities have not confirmed any connection between the two men. 

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Carl Grillmair

Carl Grillmair, a California Institute of Technology astrophysicist known for his work on exoplanets and the discovery of water on distant worlds, was shot and killed outside his California home on Feb. 16, 2026. 

Grillmair, 67, had spent decades working on major NASA-backed missions, including the Hubble and Spitzer space telescopes, contributing to research on galactic structure, dark matter and the search for habitable planets.

Authorities later arrested a 29-year-old suspect in connection with the killing, charging him with murder as well as carjacking and burglary in separate incidents. Investigators said the suspect had previously been reported for trespassing on Grillmair’s property in the weeks leading up to the shooting.

Nuno Loureiro

Nuno Loureiro, an MIT physicist and director of the university’s Plasma Science and Fusion Center, was shot at his home in Brookline, Massachusetts in December 2025 and later died. 

Loureiro, 47, was a leading figure in fusion energy research, studying plasma physics and working on technologies aimed at harnessing near-limitless clean energy.

Authorities later linked his killing to a suspect connected to a separate mass shooting at Brown University days earlier. Investigators said the suspect, who had previously attended university with Loureiro in Portugal, died by suicide after the attacks, effectively closing the case.

Officials have not indicated Loureiro’s death was connected to his research.

Frank Maiwald

Frank Maiwalk, a longtime engineer at NASA’s Jet Propulsion Laboratory, died in Los Angeles on July 4, 2024. 

The only widely available public record of Maiwald’s death is a brief online obituary.  No cause of death has been publicly disclosed, and reporting indicates no autopsy was performed.

Maiwald spent decades at JPL. His work focused on building instruments capable of detecting chemical signatures including water, organic molecules and other indicators scientists use to assess whether environments beyond Earth could support life.

Melissa Casias

Melissa Casias, an administrative employee with security clearance at Los Alamos National Laboratory, disappeared June 26, 2025. She was last seen in Taos County, New Mexico, walking alone along the side of a road. 

Her niece said earlier that day, Casias, 53, had picked up a sandwich and dropped it off for her daughter in Taos. When family members returned home, they found her car, purse, keys and both her personal and work-issued phones inside. The phones had been factory reset, wiping recent data and communications.

Family members have strongly pushed back on the idea that she left voluntarily. They said she’s been getting ready to care for their mother during an upcoming surgery.

Anthony Chavez

Anthony Chavez, a retired Los Alamos National Laboratory employee, was last seen around May 4, 2025, at his home in Los Alamos, New Mexico. 

When authorities and family members searched the 78-year-old’s home, they found his wallet, keys and other personal items left behind inside. His car was locked in the driveway, and there were no signs of forced entry or a struggle, according to the Los Alamos Reporter.

Chavez worked for decades at Los Alamos National Laboratory before retiring in 2017, placing him within the same northern New Mexico defense hub as others who also disappeared. 

Jason Thomas

Jason Thomas, an associate director of chemical biology at pharmaceutical company Novartis, went missing in December 2025 and was found dead on March 17, 2026. 

Thomas, 45, was reported missing after leaving his home in Wakefield, Massachusetts, late at night. Surveillance footage captured him walking near train tracks shortly after midnight. His phone and wallet were left at home. 

Three months later, his body was recovered from Lake Quannapowitt after the ice thawed. Officials said no foul play was suspected, though the cause and manner of death have not been publicly disclosed.

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