Jack Teixeira, the 21-year-old Air National Guardsman accused of leaking classified intelligence documents online in recent months, will appear in a Boston federal courtroom Friday morning, sources tell Fox News. 

FBI agents arrested Teixeira at his home in North Dighton, Massachusetts, Thursday without incident. Attorney General Merrick Garland said the young man is being investigated for the "alleged unauthorized removal, retention and transmission of classified national defense information." He will make his first court appearance in the U.S. District Court for the District of Massachusetts sometime Friday between 10 a.m. and 2 p.m., according to a source with the U.S. Attorney's Office for the District of Massachusetts. 

Teixeira joined the Air National Guard in September 2019 and worked as a cybersecurity systems journeyman, a position in which he held the highest level security clearance granted by the federal government for top secret information, according to an internal Department of Defense email reviewed by Fox News. 

His security clearance and access to classified government systems have since been revoked, according to another internal government document.

WHO IS JACK TEIXEIRA, THE AIR NATIONAL GUARDSMEN ALLEGEDLY BEHIND LEAKED CLASSIFIED DOCUMENTS?

Teixeira was most recently stationed at Otis Air National Guard Base in Cape Cod as a member of the 102nd Intelligence Wing. He was promoted to airman first class in July, according to the unit.

In a call with members of Thug Shaker Central, a panicked Teixeira seemed to know he was in trouble. One of the group members, who uses the screen name Vahki, recounted to The New York Times that Teixeira sounded as if he was in a speeding car the last time they spoke.

"Guys, it’s been good – I love you all," Teixeira said, according to Vahki. "I never wanted it to get like this. I prayed to God that this would never happen. And I prayed and prayed and prayed. Only God can decide what happens from now on."

Details of the leaked Pentagon documents were reported last week by The Washington Post, which obtained dozens of what appeared to be photographs showing classified intelligence briefings detailing Ukraine's combat abilities, information about the Ukrainian and Russian militaries, and highly sensitive analysis about U.S. allies and adversaries, including China. 

President Biden has said nothing leaked was "of great consequence," but White House national security spokesman John Kirby warned Wednesday, "we don't know what else this individual or individuals might have and might still release." 

"You've got highly sensitive classified information now in the public domain, and that's simply unacceptable and could do damage to our national security," Kirby said. 

FBI ARRESTS MASSACHUSETTS AIR NATIONAL GUARDSMAN JACK TEIXEIRA IN PROBE OF CLASSIFIED DOCUMENT LEAKS

The FBI began surveilling Teixeira in connection with the leaks before Thursday but were forced to accelerate their plans to arrest him after The New York Times identified him on Thursday morning, a source briefed on the investigation told Fox News. 

The report named Teixeira as the leader of a Discord group called "Thug Shaker Central" that consisted of roughly 20 to 30 young men. Discord is an instant messaging social media platform popular with gamers – members of Thug Shaker Central reportedly bonded during the pandemic by playing video games together, sharing memes and discussing guns.

Group members who spoke to the New York Times said Teixeria began posting classified documents in October, including detailed battle maps from the war in Ukraine labeled "TOP SECRET." Between October and March he reportedly posted about 350 documents to the group. His motivation appears to be wanting to inform and impress his online friends with inside knowledge of events happening abroad. 

The classified materials began circulating more widely after another member of the group posted several dozen documents to a public Discord chat called #War-Posting, according to the outlet. By April, classified U.S. intelligence on Ukraine was being posted on the Telegram messaging app by supporters of Russia's invasion of Ukraine. 

U.S. defense officials previously told Fox News the leak could be "bigger than Snowden" in terms of damage to intelligence and allied relationships.

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

Pentagon press secretary Brig. Gen. Pat Ryder called the leaks "a deliberate criminal act," saying that distribution lists for classified information are being reviewed. 

"We entrust our members with a lot of responsibility at a very early age," Ryder told reporters Thursday. 

"You've received training, and you will receive an understanding of the rules and requirements that come along with those responsibilities. And you're expected to abide by those rules, regulations and responsibility. It's called military discipline. And, in certain cases, especially when it comes to sensitive information, it also is about the law."

Fox News' Greg Norman, David Spunt, Liz Friden, Gillian Turner, Jake Gibson and Paul Best contributed to this report.

Chinese leader Xi Jinping will play host to Brazilian President Luiz Inácio Lula da Silva in Beijing on Friday, continuing the Asian country’s international diplomacy campaign which has included meetings with Russia and Saudi Arabia.

The leaders will seek to bolster ties between two of the world’s largest developing nations. The meeting comes on the heels of China already convincing Brazil to drop the use of the U.S. dollar in some international agreements.

The meeting comes on the second day of Lula’s visit to his country.

China is Brazil’s most important trading partner and ally. Their ongoing relationship falls in hand with China’s interest in challenging Western-dominated economic institutions.

ECONOMIST SOUNDS THE ALARM ON THE 'GREATEST ENEMY TO THE US DOLLAR': 'IT'S THE US TREASURY'

The state visit included a swearing-in ceremony Thursday for former Brazilian President Dilma Rousseff, who now serves as head of the Chinese-backed New Development Bank, which funds infrastructure projects in Brazil and elsewhere in the developing world.

The NDB portrays itself as an alternative to the International Monetary Fund and World Bank.

US MUST CATCH UP TO CHINA'S DIGITAL CURRENCY CAPABILITY IN ORDER TO ‘LEAD THE WORLD’: PAUL RYAN POLICY VOLUME

The Brazilian government has said the two countries are expected to sign at least 20 bilateral agreements, underscoring the improvement in relations since Lula took over in January.

China is Brazil’s biggest export market, each year buying tens of billions of dollars worth of soybeans, beef, iron ore, poultry, pulp, sugar cane, cotton and crude oil. Brazil is the biggest recipient of Chinese investment in Latin America, according to Chinese state media.

CHINA, MALAYSIA TO DISCUSS ASIAN MONETARY FUND TO REDUCE DEPENDENCE ON US DOLLAR

Lula's visit to China follows trips to Argentina and Uruguay in January and to the U.S. in February.

A key component of Lula’s international outreach is his proposal that Brazil and other developing countries, including China, mediate peace over Ukraine. His proposal, however, includes a suggestion that Ukraine cedes Crimea to forge peace, which has angered Kyiv.

China has also been active in playing a role to end the conflict, though it claims to be more objective about the situation. Beijing often makes statements supportive of Moscow.

China has refused to condemn the invasion, criticized international economic sanctions on Russia and accused the U.S. and NATO of further provocations.

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Russia and China declared a "no limits" relationship in 2022. Xi and Russian President Vladimir Putin reaffirmed this relationship in March during a meeting in Moscow.

Xi also recently met with French President Emmanuel Macron.

The Associated Press contributed to this report.