Investigators have taken an Air National Guardsman into custody in the case of leaked classified documents that shed light on the war in Ukraine and rattled the U.S. government.

Jack Teixeira, a 21-year-old member of the 102nd Intelligence Wing of the Massachusetts Air National Guard, is the leader of a small online gaming chat group where several classified documents have been leaked over the last few months. His identity was confirmed by Attorney General Merrick Garland on Thursday.

Teixeira joined the Air National Guard in September 2019 and was most recently stationed at Otis Air National Guard Base as a "Cyber Transport Systems Journeyman." 

He held the highest-level security clearance granted by the government to review top secret information, according to an internal Department of Defense email reviewed by Fox News. 

US DEFENSE SECRETARY LLOYD AUSTIN SAYS LEAKED CLASSIFIED DOCUMENTS WERE 'SOMEWHERE IN THE WEB'

Selfie of Jack Teixeira, the 21-year-old National Guard Airman accused of leaking classified information.

Cyber transport systems workers ensure that the underlying infrastructure of the Air Force’s global communications network is operating properly. Employees are required to have a high school diploma or GED, knowledge of electronics, experience in the installation of network infrastructure, and 7.5 weeks of basic military training. 

Applicants are also required to pass a Single Scope Background Investigation, which is a government-wide investigation of those who need to access top secret material. 

PENTAGON DOCUMENT LEAK HAS IMMEDIATE IMPACT ON NATIONAL SECURITY: SUCKS UP ‘A LOT OF OXYGEN’

The private Discord group that Teixeira led, Thug Shaker Central, comprised 20 to 30 mostly young men and teenagers who shared memes and talked about love of guns and video games.

A member of the group first posted hundreds of pages of intelligence briefings to the chat a few months ago, telling its members that it was important for them to stay up to date on world events.

Some members of the Thug Shake Central group defended Teixeira, arguing that the young Guardsman only posted the materials to the group in an attempt to spark discussion and keep friends informed.

"This guy was a Christian, anti-war, just wanted to inform some of his friends about what’s going on," a 17-year-old member of the group told The New York Times. "We have some people in our group who are in Ukraine. We like fighting games, we like war games."

SOUTH KOREA SAYS LEAKED PENTAGON DOCUMENT SUGGESTING US SPYING IS ‘UNTRUE’ AND ‘ALTERED’: REPORTS

Members of the group said the leaked documents didn't begin to receive attention until one member of the group posted some of them to a public online forum, where they were then picked up by Russian-language Telegram channels.

The members who spoke to The New York Times described Teixeira as older than most of the other members of the group and was the group's "undisputed leader." One of the members said he has known Teixeira for three years and met him in person, while another told the outlet that Teixeira had access to classified documents due to his role in the Air National Guard.

It is unclear how the young airman gained access to the documents and whether someone in his position and grade would have access to them.

Federal agents showed up to the Teixeira property in armored vehicles Thursday. About half a dozen armed agents wearing tactical gear spilled out and cordoned off the area around the home, eventually taking him into custody.

"Today, the FBI took 21-year-old Jack Douglas Teixeira into custody without incident at a residence in North Dighton, Massachusetts, for his alleged involvement in leaking classified U.S. government and military documents," the FBI said in a statement. 

"The FBI is continuing to conduct authorized law enforcement activity at the residence," the statement added. "Since late last week the FBI has aggressively pursued investigative leads and today's arrest exemplifies our continued commitment to identifying, pursuing, and holding accountable those who betray our country's trust and put our national security at risk."

CLICK HERE TO GET THE FOX NEWS APP 

The leaked documents revealed sensitive information about the war in Ukraine, including warnings that China was considering giving Russia military aid and secret plans by South Korea to deliver more than 300,000 rounds of ammunition to Ukrainian forces.