What Is 'Hell Week'? Navy SEAL Training in Which Candidate Kyle Mullen Died

The Navy on Sunday identified the SEAL candidate who died just hours after completing what is known as Hell Week, a brutal operational training phase that tests mental and physical endurance.

Seaman Kyle Mullen, 24, of New Jersey, died on February 4 at Sharp Coronado Hospital in Coronado, California, the Navy said.

The cause of his death is under investigation. He and another Navy SEAL trainee were hospitalized after they both reported experiencing symptoms of an unknown illness. The other trainee, who hasn't been named, is reportedly in a stable condition.

What Is 'Hell Week'?

Mullen's death came shortly after he had completed the Navy's Hell Week, which it describes as "the defining event" of training for the elite Basic Underwater Demolition/SEAL (BUD/S) class.

It takes place in the third week of first phase of training, and consists of five and a half days of "cold, wet, brutally difficult operational training" on fewer than four hours of sleep, according to the official website of the Navy SEALs.

Described as the toughest training in the U.S. military, on average only 25 percent of SEAL candidates make it through Hell Week.

"Hell Week tests physical endurance, mental toughness, pain and cold tolerance, teamwork, attitude, and your ability to perform work under high physical and mental stress, and sleep deprivation," its website states. "Above all, it tests determination and desire."

SEAL candidates are made to perform tasks such as running, swimming, paddling, carrying boats on their heads, doing log PT, sit-ups, push-ups, rolling in the sand, slogging through mud, paddling boats and doing surf passage, on little sleep.

The Navy says candidates are trained during Hell Week to carry out missions that require them to think, lead, make sound decisions, and functionally operate when they are extremely sleep-deprived, approaching hypothermia, and even hallucinating.

Instructors push and assess trainees to determine who has the physical ability and character to save their and other teammates' lives.

The grueling training week tests mental strength as much as it does the physical side.

Rear Adm. H.W. Howard III, the commander of Naval Special Warfare Command in Coronado, California, issued a statement offering his condolences to Mullen's family.

"We extend our deepest sympathies to Seaman Mullen's family for their loss," Howard said. "We are extending every form of support we can to the Mullen family and Kyle's BUD/S classmates."

Mullen was a former football star for Yale & Monmouth University, and joined the Navy in March 2021. Mullen reported to SEAL training in Coronado in July, the San Diego Union-Tribune reported.

The Navy said he and the other hospitalized SEAL candidate didn't experience an accident or unusual incident during their Hell Week training, the AP reported. Mullen was not actively training at the time of his death, the Navy said.

Navy SEALs Hell Week training
Navy SEAL candidates take part in Hell Week, a brutal operational training phase that tests mental and physical endurance. Seaman Kyle Mullen, 24, of New Jersey, died on February 4 at Sharp Coronado Hospital in Coronado, California, hours after completing the training. Richard Schoenberg/Corbis/Getty Images