Retired Marine General Found Dead at Twentynine Palms Died of Natural Causes, Autopsy Shows

A retired Marine Corps general whose body was found aboard Marine Corps Air Ground Combat Center Twentynine Palms, California, in June died of natural causes, an autopsy report obtained by Military.com through a public records request found.

Retired Maj. Gen. William Mullen, 59, was found by staff at the base's Roadrunner Inn, where he was staying in temporary lodging, according to the report. He was due to check out at 11 a.m. but did not, prompting staff to check on him by prying open the door to his room.

Paramedics responded to the scene that afternoon and confirmed that Mullen had passed away at 1:39 p.m. June 29, the report said, adding that "there were no resuscitation efforts made."

Read Next: Marine Corps Lays Out Plan for Harrier Crews as Stalwart Aircraft Flies into Sunset

The autopsy, which was conducted by the San Bernardino County Sheriff's Department coroner, found that a blood clot, also known as a deep vein thrombosis, in Mullen's left leg dislodged and traveled to his lungs, blocking the left and right sides of his pulmonary arteries, a condition also known as a pulmonary embolism.

The Naval Criminal Investigative Service told Military.com on Tuesday that the investigation into Mullen's death is ongoing, but would not comment on specifics or the autopsy findings.

"With regards to investigative timelines, there is no timeline for death investigations as each is different," Jeff Houston, a spokesperson for NCIS, said in an email to Military.com. "Death investigations take several months to complete at a minimum and sometimes can take more than a year to complete, depending on the circumstances of the investigation."

A Mullen family member also declined to comment.

The report, which included a document titled "coroner investigation," noted that Mullen's bags were packed and organized "as if he was leaving the premises."

Mullen was at the combat center to attend the change of command ceremony for the Marine Corps Tactics and Operations Group, or MCTOG, which occurred the day prior to his death, a spokesperson for Twentynine Palms told Military.com on Wednesday.

The autopsy noted that Mullen did not have a diagnosed medical history, but had been to a doctor prior to his death due to "some lung issues" and a bad cough, the report said, citing his next of kin. The doctor cleared him but prescribed an inhaler after "he had been unable to breathe properly," the autopsy said.

Mullen's family has a history of heart problems, the report added, but was otherwise "known to be healthy."

"There are also genetic conditions which can increase the risk of clot development, and it is possible that Mr. Mullen had a genetic condition which predisposed him to the development of blood clots," the autopsy stated, after it ruled out trauma, obesity or cancer, for example, and noted that the "underlying cause of the blood clots in the left lower extremity is unknown."

Dr. Carlos Mena-Hurtado, an associate professor of medicine (cardiology) at Yale University, reviewed part of the report with Military.com over the phone Wednesday and confirmed that the clot caused a "massive pulmonary embolism," resulting in the retired general's death.

"There are multiple risk factors," Mena-Hurtado said of pulmonary embolisms in general. "There are mechanical risk factors, like being immobile, like a fracture, like having recent surgeries, being in a wheelchair for long periods of time -- so anything that has immobility becomes a source or a risk for clots in the legs."

The pulmonary arteries transport oxygen-depleted blood from the heart to the lungs for oxygenation, according to the National Institutes of Health. Roughly 1 to 3 in every 1,000 adults in the U.S. develop deep vein thrombosis, also known as DVT or pulmonary embolism, each year, according to the Cleveland Clinic. Men are likely to experience recurrent instances of DVT, according to the NIH.

Other risk factors include blood illnesses, protein deficiencies or blockages in the leg veins, Mena-Hurtado added. Air travel -- especially involving long-distance or lengthy flights during which a traveler sits for extended periods -- can lead to DVTs, according to the Mayo Clinic. DVTs are the most common cause of pulmonary embolism, according to the facility.

"It's unpredictable. There's not necessarily an age cutoff," Mena-Hurtado said. "The age is linked to the potential cause, like if you break a leg -- whether you do it at the age of 10 or at the age of 80 -- you're at risk for it. If you have some genetic predisposition, more likely than not, it will show up at an earlier age."

Mullen was the commander of Twentynine Palms starting in 2016. He was an artillery officer and made multiple deployments to Iraq during a 34-year career in the Marine Corps. He retired in 2020, having served as the commanding general of the Marine Corps' Training and Education Command as his last billet.

"Maj. Gen. Mullen's dedicated service to our nation and the Marine Corps will always be remembered," Maj. Gen. Thomas Savage, head of the Marine Air Ground Task Force Training Command, said in a statement shared with Military.com in July. "Our thoughts and prayers are with his loved ones."

-- Patricia Kime contributed to this report.

Related: Retired Marine Major General Found Dead at Twentynine Palms; Investigation Ongoing