What to know about the missing scientists alarming Congress

• Chairman James Comer (R-Ky.) and Rep. Eric Burlison (R-Mo.) sent letters to FBI Director Kash Patel, NASA administrator Jared Isaacman, Energy Secretary Chris Wright and Defense Secretary Pete Hegseth, seeking information on the deaths and disappearances, and "the processes and procedures in place to protect American scientific secrets and ensure personnel safety."

What prompted the probe?

The committee's letter did not cite a specific reason for the investigation, but referenced "unconfirmed public reporting" on the cases, including the recent disappearance of retired Air Force Maj. Gen. William Neil McCasland.

• McCasland, who worked at various military labs, was last seen at his Albuquerque home in February. He was involved in aerospace research throughout his career, but had been retired for 13 years, per a Facebook post from his wife.
• McCasland left home with his wallet and a gun but left behind his phone, prescription glasses and wearable tech devices. He had cited "mental fog" when leaving several research groups, Lt. Kyle Woods of the Bernalillo County Sheriff's Office said at a news conference.

Who is among the missing or deceased?

All the missing or deceased have connections to the U.S. nuclear and aerospace systems or laboratories.

• Deepening the mystery are the locations where the deaths or disappearances occurred. Four cases are in California, four in New Mexico, and two in Massachusetts.

Zoom in: Michael Hicks, Frank Maiwald, and Monica Reza were all scientists at NASA's Jet Propulsion Laboratory in California. There is no indication that they worked on the same projects.

• Hicks died in 2023 and Maiwald in 2024, while Reza went missing in June 2025.
• Reza and McCasland both worked at Kirtland Air Force Base in the early 2000s, per the New York Post, but there is no evidence they worked together on any projects.
• A fourth scientist, Caltech astrophysicist Carl Grillmair, died in February. Caltech manages the JPL lab.

In New Mexico, Anthony Chavez, Melissa Casias, and Steven Garcia all disappeared within four months of one another in 2025.

• Chavez and Casias both worked at the Los Alamos National Laboratory, while Garcia worked at the New Mexico division of the Kansas City National Security Campus.
• None of their jobs involved scientific research. Like McCasland, Garcia left his home with a gun, NewsNation reported.

MIT professor Nuno Loureiro was killed outside his home in Brookline, Mass., in December 2025. Pharmaceutical scientist Jason Thomas disappeared the same month, though his body was found in March.

Was foul play involved?

Despite allegations from online sleuths and some media reports, several of the deaths don't appear to have any connection to their careers.

• Alleged killer Claudio Valente and Lourerio graduated from the same university in Portugal, and authorities said Valente described decades-old grudges in videos.
• The suspect in Grillmair's shooting was a neighbor with a history of erratic behavior who had previously trespassed on Grillmair's property.
• Thomas was struggling with the recent deaths of his parents when he disappeared, his wife told Dateline.
• Hicks' cause of death was never publicly confirmed, but his daughter told CNN he had medical problems and "there's no train of logic to follow that would implicate him in this potential federal investigation."
• There is no public information regarding Maiwald's death.

What happens next

Speculation continues, but even Comer is on the fence about what this all means.

• Speaking to NewsNation, Comer said the cases could be connected and the "usual suspects" like China, Iran, Russia, and North Korea were all under scrutiny.
• "But there are a lot of, you know, Eastern European countries and other countries that could be involved as well, or it could be a coincidence," he added.

The Oversight Committee asked for briefings by Patel, Hegseth, Wright, and Isaacman no later than April 27.