An Air Force veteran who agreed to testify before Congress about secret government UFO programs died just months before the hearings of an accidental drug overdose, The Post has learned.

Matthew James Sullivan, 39, died at his home in Falls Church, Va., on May 12, 2024 from a lethal mix of alcohol, alprazolam, cyclobenzaprine and imipramine, according to the Northern District Office of the Chief Medical Examiner.

Alprazolam is generic Xanax, an anti-anxiety medication; cyclobenzaprine is a powerful prescription muscle relaxant that works on the central nervous system; imipramine is a drug for children used to treat anxiety and bedwetting.

The mysterious death is of “grave concern” to Rep. Eric Burlison (R-Mo.), who referred the matter for investigation to the FBI due to “implications for national security,” according to a letter obtained by The Post.

The FBI indicated in a statement that Sullivan’s death could be under investigation along with the dozen other missing or dead US scientists.

“While we do not comment on specific incidents, the FBI is spearheading the effort to look for connections into the missing and deceased scientists. We are working with the Department of Energy, Department of War, and with our state and local law enforcement partners to find answers,” the FBI said.

Sullivan earned a Bronze Star for valor in Operation Enduring Freedom and later worked for the Air Force Intelligence Agency, National Air and Space Intelligence Center, and the National Security Agency, according to an obituary.

Sullivan held “the burden that a select few in this nation have of truly understanding what’s going on,” retired Major Gen. David Abba, who served as director of special programs and later as director of the Department of Defense Special Access Program Central Office said at the funeral.

Sullivan was part of a so-called legacy UFO program — the US government’s crash retrieval program — that has operated for decades in the shadows across several executive branch agencies, sources told The Post.

Sullivan had personally seen UFOs in the federal government’s possession and would have exposed the legacy program at the congressional hearing in November 2024, according to sources.

Other UFO whistleblowers have also faced threats to their safety after coming forward with world-shattering information.

David Grusch, an Air Force and intel community veteran who testified to congress in 2023 that the US was in possession of UFOs and non-human “biologics,” wrote a letter in May 2022 to the Intelligence Community Office of Inspector General, claiming he faced harsh reprisals after reporting evidence of UFOs.

Grusch further claimed he received credible death threats before his revelations to the American public.

A version of Grusch’s letter was sent to the IC OIG and included information regarding Sullivan’s death, sources said.

The agency told The Post, “IC OIG can neither confirm or deny the existence of any ongoing or potential investigations.”