Marine Corps Capt. Daniel Kult, left, Sgt. John Dietrick, center, and Pfc. Alexander Meinhardt restrained a passenger on a flight from Tokyo.
CNN  — 

Three US Marines stepped in to detain a passenger who allegedly made threatening comments during a flight from Japan to Texas.

Capt. Daniel Kult, Sgt. John Dietrick, and Pfc. Alexander Meinhardt were headed to Texas from Tokyo on Monday when a passenger on their flight barricaded himself inside a bathroom and began screaming, according to an online statement from the Marine Corps.

Dietrick said that even through the headphones he was wearing he could hear someone inside the bathroom who sounded “distraught.”

That’s when the three Marines gathered outside the restroom while a flight attendant unlocked the door, according to the release. Once it was open, the Marines restrained the passenger with flex ties.

“I knew I had to step in when he became a danger to others and himself,” Meinhardt said. “I didn’t think twice about helping restrain him through the rest of the flight.”

After securing the passenger to a seat, the marines kept their eyes on him for the remainder of the flight.

It’s unclear why the passenger was distraught.

“At this time we cannot identify the airline or comment on the disposition of the passenger, as the incident remains under investigation,” Marine spokeswoman 2nd Lt. Kayla Olsen told CNN.

The flight eventually arrived at Dallas Fort Worth International Airport after initially being diverted to Los Angeles International Airport so the passenger could be transported to a local hospital for a mental evaluation, the release said.

The US Attorney’s Office for the Central District of California and the FBI continue to investigate the incident, according to the release.