A Navy junior officer died Sunday during a joint training exercise with Marines at a base in Hawaii, officials said.

Aaron Fowler, 29, became unresponsive during the training at the Marines’ Kanehoe Bay base and died at a hospital, military officials said in a press release Wednesday.

The nature of the deadly incident was not disclosed and was under investigation by NCIS and local authorities, the Navy said.

Fowler was a junior grade lieutenant assigned to Explosive Ordnance Disposal Mobile Unit One, a San Diego-based outfit tasked with clearing explosive hazards, according to the release.

“Our deepest sympathies go out to Aaron’s family and friends, and we join them in remembering and mourning this brave warrior,” said Rear Adm. Joseph Diguardo, Jr., commander, Navy Expeditionary Combat Command.

“His decision to join this elite special operations community was a testament to the dedicated and selfless character he embodied and his legacy will endure in our ranks through those he inspired by his service.”