The United States Federal Bureau of Investigation (FBI) has confirmed it is leading a coordinated government effort to determine whether any connections exist among at least ten deaths and disappearances of researchers and officials linked to nuclear science, aerospace, and classified defence programmes over the past four years, as the House Oversight Committee opens a formal congressional inquiry.
In a statement, the FBI said it “is spearheading the effort to look for connections into the missing and deceased scientists,” adding that it is working alongside the Department of Energy, the Department of War, and state and local law enforcement partners. FBI Director Kash Patel said investigators are examining whether any links exist to classified access or foreign actors and that if evidence of nefarious conduct or conspiracy emerged, arrests would follow.
The House Oversight Committee sent letters to FBI Director Patel, Secretary of Energy Chris Wright, Secretary of War Pete Hegseth, and National Aeronautics and Space Administration (NASA) Administrator Jared Isaacman, requesting staff briefings by April 27. Committee Chairman James Comer and Representative Eric Burlison, who chairs the Subcommittee on Economic Growth, Energy Policy, and Regulatory Affairs, said the deaths and disappearances could “represent a grave threat to U.S. national security and to U.S. personnel with access to scientific secrets.” President Donald Trump described the matter as “pretty serious stuff,” while saying he hoped the pattern was “coincidence.”
Among the cases drawing scrutiny is the February 2026 disappearance of William Neil McCasland, 68, a retired United States Air Force Major General who commanded the Air Force Research Laboratory. McCasland walked out of his Albuquerque, New Mexico home on February 27, leaving his phone, prescription glasses, and wearable devices behind, but taking his wallet, hiking boots, and a firearm. The FBI joined the search in March.
Other cases include Michael David Hicks, a scientist at NASA’s Jet Propulsion Laboratory (JPL) who studied comets and asteroids and died in July 2023; Frank Maiwald, a space research specialist affiliated with JPL who died in Los Angeles in 2024; and Monica Reza, 60, director of JPL’s Materials Processing Group and an aerospace engineer who disappeared while hiking in Los Angeles County in June 2025. In December, Nuno Loureiro, a professor of nuclear science and engineering at the Massachusetts Institute of Technology (MIT) and director of its Plasma Science and Fusion Center, was killed at his Brookline, Massachusetts home by a former engineering classmate. The suspect later carried out a mass shooting at Brown University. In February 2026, astrophysicist Carl Grillmair, who collaborated extensively with NASA, was shot and killed outside his home near Los Angeles. A suspect was arrested who authorities say did not know Grillmair.
Authorities and experts have urged caution. NASA said in a statement that “at this time, nothing related to NASA indicates a national security threat.” The Department of War told Congress it has “no active national security investigations of any reported missing person who was a current or former DoW clearance holder and involved in special access programs.” McCasland’s wife wrote publicly that it was “quite unlikely that he was taken to extract very dated secrets from him,” adding that her husband had held only commonly held security clearances for more than a decade since his retirement.
Security analysts have noted that more than 700,000 people hold top-secret clearances in United States aerospace and nuclear sectors, meaning deaths and disappearances across that population over four years are statistically expected regardless of cause. Investigators working on the individual cases have said they see no links between them. No confirmed connection among any of the cases has been established.
