Air Force National Guard airman Jack Teixeira was charged and arrested Thursday for leaking classified documents about the war in Ukraine.

The FBI reportedly tracked down the 21-year-old through the social media account he allegedly used on the popular platform Discord to post the information.

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How did the FBI use social media? USA Today reported that the owner of the social media account leaking information would speak “by video chat or voice calls,” which helped reveal the social media user to be a “white male in his 20s” who “called himself Jack, lived in Massachusetts and worked for the Air National Guard.”

Teixeira allegedly would share several documents a week under the social media username “OG,” by uploading pictures of the documents, which “also exposed OG to greater risk. In the background of some images, they could see items and furniture that they recognized from the room where OG spoke to them via video on the Discord channel,” according to National Review.

The Deseret News reported that FBI agents took Teixeira into custody Thursday afternoon.

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What exactly is Teixeira charged with? The Associated Press reported that Teixeira has been charged with “unauthorized removal of classified national defense information,” according to Attorney General Merrick Garland.

The documents that were leaked on social media contain material obtained through “eavesdropping on key allies and adversaries and blunt assessments on the state of the Ukraine war,” according to CNN.

Fox News reported that even though the documents didn’t reveal much about the war and don’t seem to have a “chain-of-custody,” the motive for the leak is still unknown and some are waiting for more information to come out before deciding on why the leak happened.

The leak reportedly is a “very serious” risk to national security that includes files with a “format similar to documents issued to senior leaders.”