The two sailors were quickly taken to local hospitals hours after they began showing symptoms of illness.

On Sunday, the Navy identified Seaman Kyle Mullen, 24, of Manalapan, New Jersey, as the deceased SEAL candidate. He was assigned to Naval Special Warfare Basic Training Command in San Diego, California.

“We express our deepest condolences to Seaman Mullen’s family for their loss,” Rear Admiral HW Howard III, commander of Naval Special Warfare Command, said in a statement.

Mullen was pronounced dead at 5:42 p.m. Pacific Standard Time Friday at Sharp Coronado Hospital in San Diego, officials said. The cause of his death is still under investigation.

The name of the hospitalized SEAL candidate has not been released, but they are in stable condition at Naval Medical Center in San Diego, officials said.

“Two SEAL candidates, assigned to Naval Special Warfare Basic Training Command, were taken to hospital Feb. 4 several hours after their Basic Underwater Demolition SEAL (BUD/S) class successfully completed Hell Week, which is part of of the Navy’s first phase. SEAL Evaluation and Selection Pathway,” a statement from Navy Special Warfare Command said.

“We are all saddened by the unfortunate passing of Kyle Mullen. As part of our 2019 Championship team, he will be remembered not only as a great player, but also as a great person and a great teammate,” said Kevin Callahan, the head football coach at Monmouth University, where Mullen played football, in a statement. “He was highly motivated on the pitch, but his maturity, intelligence and concern for his teammates is what Kyle shines through. On behalf of President Leahy and the entire Monmouth University community, we would like to extend our condolences to the Mullen family their loss.”

Hell Week is the famous end of the first phase of BUD/S training where sailors who want to be SEALs are pushed to the limit of physical and mental exhaustion through a series of intense workouts. More than half of SEAL candidates who go through Hell Week do not complete the grueling week of training that allows them to continue through the six months of SEAL training.

“Both Sailors were not actively training when they reported symptoms and were transported for emergency treatment,” the Navy statement added.

The last Navy SEAL candidate to die during BUD/S training was Seaman James Lovelace, 21, who drowned in a swimming pool during his first week of training in May 2016. After his drowning, the Navy instituted additional safety protocols for the swim program. .

“SEAL training takes you beyond your personal limits,” said former SEAL and ABC News contributor Eric Oehlerich. “It’s designed to push you beyond your perception of what’s possible, shattering the glass ceilings of what you’re capable of both mentally and physically.”

Oehlerich said he believes the challenging training of future SEALs is conducted within proven medical limits and led by highly trained professional instructors, but he acknowledged that all types of military training carry risk.

“From time to time, deaths occur in training. Although tragic, joining the training program keeps SEALs alive in combat,” he said. “It’s necessary, it doesn’t get diluted.”

“Condolences to the intern’s family,” Oehlerich said. “They will always be part of the community and we will always be there as much as possible.”