A 21-year-old US airman has been arrested and charged with unauthorised removal and transmission of classified information relating to national security issues, including the Ukraine war.
Jack Teixeira was arrested at his family home in Dighton, rural Massachusetts, by the FBI, and will appear in court in Boston on Friday.
The leaked documents were first posted on an online chat group, which Mr Teixeira was identified as the leader of.
They revealed sensitive secrets about American allies, embarrassing Washington and raising concerns about the security of classified information.
Mr Teixeira worked as an IT specialist in the intelligence wing of the Massachusetts National Guard, and held the rank of Airman 1st Class, a relatively junior position.
While it is not clear what level of security clearance he held, it is reportedly required for access to top-secret information.
The Pentagon says it will re-examine how classified information is distributed, but a spokesman said it was “the nature” of the US military to entrust young service members with high levels of responsibility.
The motive for the leak is thought to be unusual, as Mr. Teixeira was neither a whistleblower nor a foreign agent. Friends said he had a skepticism of government but was not typically outspoken.
The suspect was taken into custody without incident, and Attorney General Merrick Garland provided no further details on the investigation or motive for the leaks.
Meanwhile, Defense Department spokesman Brigadier General Pat Ryder described the leak as a “deliberate criminal act”.
The leaked documents were posted on Discord, a social media platform popular with gamers, and were seen by at least 50 people, and possibly more than 100, before being spotted by Pentagon officials.