Air National Guardsman Jack Teixeira was arrested Thursday over his alleged role in leaking secret files from the Pentagon that have embarrassed U.S. allies and cast doubt on Ukraine’s ability to succeed in its war with Russia.

The arrest came hours after President Biden said on Thursday the U.S. is “getting close” in the investigation to finding the source of the largest government records leak in a decade.

The New York Times reported earlier Thursday that Teixeira, 21, was the leader of the Discord server where the files were shared and is an Airman First Class with the 102nd Intelligence Wing of the Massachusetts Air National Guard.

A hundred or more of the documents are thought to exist, detailing everything from Russian and Ukrainian battlefield assessments to affairs across U.S.-allied nations.

Here’s everything we know about Teixeira and the investigation into him.

What officials are saying

It’s unclear how Teixeira had access to highly classified information. 

Attorney General Merrick Garland said Teixeira was suspected of “unauthorized removal, retention and transmission of classified national defense information.”

“FBI agents took Teixeira into custody earlier this afternoon without incident. He will have an initial appearance at the US District Court for the District of Massachusetts.”

Pentagon press secretary Air Force Brig. Gen. Pat Ryder declined to comment on the Justice Department’s investigation and on Teixeira at a Thursday briefing.

But speaking more broadly, Ryder said the leak was a “deliberate, criminal act” and those with security clearances should know better.

“You receive training and you will receive an understanding of the rules and requirements that come along with those responsibilities,” he said. 

“You’re expected to abide by those rules, regulations and responsibility. It’s called military discipline,” he continued. “And in certain cases, especially when it comes to sensitive information, it also is about the law.”

Group leader allegedly shared intel for years

In 2020, a group of online friends connected by a shared enthusiasm for guns and military gear started a server on Discord, a chat forum site primarily used for gaming, The Washington Post reported.

The leader of the Discord group, known as “OG,” worked at an unidentified military base and began sharing transcribed notes of classified intelligence with the server, called “Thug Shaker Central,” which hosted up to 30 members, per the Post’s report.

The Post report did not name Teixeira, but a later New York Times report identified him as the leader of the group. In a July 2022 Facebook post, the 101st National Guard congratulated Teixeira for his promotion to Airman 1st Class at Joint Base Cape Cod.

OG claimed to spend part of his time in a secure government facility that prohibited cell phones and cameras. He was generally revered by the online server group and touted his access to classified secrets, according to The Post.

But interest in the secrets waned over time in the server. Toward the end of last year, OG, who railed against U.S. corruption and shared right-wing ideology, shifted to taking pictures of the classified documents to maintain the group’s attention on government secrets, per The Post.

Documents first appear in March 

Pictures of the classified documents first appeared outside of Thug Shaker Central in early March, investigative group Bellingcat reported.

A batch of 10 documents surfaced on a Discord server called “Minecraft Earth Map” after a user posted them.

Bellingcat traced an earlier leak to a Discord server called “WowMao,” which appears to have been sourced from the Thug Shaker Central channel.

The documents were never supposed to leak out of the original server, according to The Times and The Post, which spoke to members of the original Discord server.

The New York Times set off firestorm

Last week, The New York Times first reported that classified Pentagon documents were circulating online, quickly garnering the world’s attention.

The documents were now being shared on Telegram and Twitter, breaking out of obscure chat forum sites and into the more public online world, where Russian sources also got their hands on them.

The first batch documents revealed the Pentagon’s insider information on battlefield assessments in the war in Ukraine. One of the documents, which later proved to have been altered, picked up widespread attention after it showed lower Russian casualty rates and high Ukrainian deaths in the war.

The Pentagon last Friday said it was reviewing the document leaks and on Sunday turned over a formal investigation to the Justice Department.

Ongoing vulnerabilities

Michael Butler, a professor of political science at Clark University who specializes in foreign policy and security studies, said the document leaks have underscored what may be a “systemic weakness” and vulnerability in the Pentagon.

“Information is highly decentralized [and] can be moved very easily and quickly at no cost,” Butler said, and actors “are able to exploit vulnerabilities in the system before the Department of Defense or intelligence agencies can close them again.”

The Pentagon has reportedly started to limit who has access to classified material and briefings since the leak occurred, and defense officials say they are reviewing policies around information sharing.

Lawmakers on both sides of the aisle has been pushing the Pentagon for answers on how the leaks occurred, and how it plans to stop them moving forward.

Rep. Jim Himes (D-Conn.) told CNN Wednesday he received few answers during a non-classified briefing on Wednesday, and worried about the impact the leaks would have on U.S. relationships abroad.

“For all the soothing tones that I heard from the secretary of state, if I were an ally right now, I would be wondering whether the United States can keep their secrets safe.”