The FBI has arrested Massachusetts Air National Guardsman Jack Teixeira, 21, for allegedly leaking dozens of sensitive US intelligence documents in the biggest national security breach in at least a decade.

Teixeira was taken into custody on Thursday at his home in North Dighton, Mass., following the disclosure of sensitive information that pertained to the war in Ukraine — and detailed US intelligence gathering on allies like Israel and South Korea.

The Guardsman is an enlisted member of the 102nd Intelligence Wing located at Joint Base Cape Cod.

As law enforcement officials closed in on Teixeira, the young man read a book on his home’s patio, seemingly unaware of what was about to happen.

The arrest came after the New York Times identified Teixeira as a person of interest in the case, which was opened last week when some of the shared documents were discovered on Russian Telegram channels.

Reports indicate Teixeira was a prominent figure in The “Thug Shakers Central” Discord group, where the documents initially appeared.

What information is in the leaked documents?

The classified documents from the Department of Defense contained key information about America’s espionage efforts against Russia, as well as details about Ukraine’s military planning.

A Ukrainian official told CNN that the leaked documents had specific information about a counterattack his nation was planning against Russia, forcing military leaders to change their battle strategy.

The intelligence also suggested China could arm Moscow should Zelensky go through with plans to launch military attacks inside Russia.

The documents also highlighted persistent rumors that Russian President Vladimir Putin is undergoing chemotherapy and that his officials would use his absence to “throw” the war.

Other intelligence detailed qualms among South Korean officials about a US request for Seoul to send ammunition that Washington would then send on to Kyiv.

South Korea, also an American ally, has a policy against arming foreign nations at war.

The documents also highlighted America’s effort to get Israel to help Ukraine, despite the country remaining officially neutral in the conflict.

The files suggested America could push Israel to sell weapons to a third-party that would arm Ukrainian forces, allowing the Jewish state to maintain the appearance of advocating for peace.

How were the documents leaked?

The classified pages were disseminated on the small Discord channel, Thug Shaker Central, linked to fans of the YouTuber Oxide.

Channel members would often give their thoughts on the war, until one person began posting pictures of themselves holding the classified documents.

The pages were marked “secret,” have fold marks on them, and appeared to be taken on top of a home desk or table.

The files spread from there to a second Discord group linked to fans of YouTuber “wow_mao”.

The leak grow when a member of that channel posted some of the documents to a bigger channel called “Minecraft Earth Map.”

What is Thug Shaker Central?

The private Discord channel is composed of about 20 to 30 people who were fans of YouTuber Oxide before being ousted from his main Discord fan channel for allegedly spreading homophobic and racist posts.

According to the Washington Post, the name Thug Shaker refers to an online meme taken from a gay porn video the trio used for amusement.

Oxide, who reportedly serves in the Army in the Pacific Northwest, told the outlet none of the leaked documents were shared on his Discord channel and he doesn’t know who leaked them.

“I can’t risk any of this,” he told the Washington Post.

“I’ve got my own clearance to watch out for.”