Cell phone video shows the moment two men threw punches at one another while on board a flight heading from Tokyo to Los Angeles.

The violent brawl broke out just before an All Nippon Airways (ANA) plane made the 11-hour flight from Narita International Airport to Los Angeles International Airport on Monday evening. The incident, which was captured on video by another passenger, Corey Hour, was uploaded to social media and has since gone viral.

“It was literally out of nowhere,” Hour said of the fight. He said he believes the altercation began when the man in the red Hawaiian shirt pointed at the other man and asked where he was from, though it is unclear what may have triggered him or made him so irate.

The two men then began throwing punches across rows of seats as those around them tried to escape the area.

“Someone help!” the man in the black shirt can be heard yelling in the video. “This guy is crazy!”

“I’ll kill you!” the man in the red shirt yells back.

A female airline employee attempted to intervene and separate the two men, at which point the man in the red shirt shook her off and continued throwing punches. The man walked away but soon came back and continued swinging at the other passenger.

Hour said that’s when he stopped filming and intervened.

“It was intense, and we had to step in,” he told the Washington Post.

“You think I’m crazy? What about the government!” the man in the red shirt yelled at Hour. He was eventually removed from the flight and arrested by local law enforcement.

The man, who has only been identified as being a U.S. citizen in his 40s, also allegedly choked an ANA employee, according to Japan Today. He was charged with assault.

As of Wednesday afternoon, he is still in custody in Japan, a police spokesman said.