FBI agents arrest Jack Teixeira, an employee of the US Air Force National Guard, in connection with an investigation into the leaks online of classified US documents, outside a residence in this still image taken from video in North Dighton, Massachusetts, US, April 13, 2023. ( Photo: Reuters)

The arrest at his home in Massachusetts comes a week after the leaks first became widely known, setting Washington on edge about the damage they may have caused.

The episode embarrassed the US by revealing its spying on allies and purported Ukrainian military vulnerabilities. 

The leak of documents, posted largely on social media sites, was believed to be the most serious security breach since more than 700,000 documents, videos and diplomatic cables appeared on the WikiLeaks website in 2010.

The Justice Department opened a formal criminal probe last week, after a referral from the Defense Department, which called the leak a “deliberate, criminal act.” 

The leaks revealed information about allies including Israel, South Korea and Turkey. 

US officials believe most of the materials are genuine. Some, however, appear to have been altered to show inflated estimates for Ukrainian battlefield casualties in the conflict with Russia as well as understated numbers for Russian forces.