Air National Guardsman accused in military records leak to appear in court by ERIC TUCKER, TARA COPP and MICHAEL BALSAMO

WASHINGTON — A Massachusetts Air National Guardsman arrested in the leak of highly classified military documents is expected in federal court Friday as the Justice Department prepares to outline the criminal case against him.

Jack Teixeira, 21, was arrested by heavily armed tactical agents on Thursday following a weeklong criminal investigation into the disclosure of highly sensitive government records, an alarming breach that exposed to the world unvarnished secret assessments on the war in Ukraine, the capabilities and geopolitical interests of other nations and other top national security issues.

Justice Department prosecutors are expected to reveal new details about the allegations while unsealing a criminal complaint in Boston charging Teixeira under an Espionage Act provision that makes it a crime to remove, retain or transmit national defense information. It was not immediately clear if Teixeira had a lawyer who could comment on his behalf.

Jack Teixeira, a member of the Massachusetts Air National Guard, was arrested in North Dighton, Massachusetts, in connection with the leaked documents probe.

Investigators believe Teixeira was the leader of an online private chat group where the documents were shared. Though prosecutors have not revealed a possible motive, accounts of those in the chat group have depicted Teixeira as motivated more by bravado than ideology.

The Biden administration has scrambled to contain the potential diplomatic and military fallout from the leaks since they were first reported last week, moving to assure allies and assess the scope of damage.

The classified documents – which have not been individually authenticated by U.S. officials – range from briefing slides mapping out Ukrainian military positions to assessments of international support for Ukraine and other sensitive topics, including under what circumstances Russian President Vladimir Putin might use nuclear weapons.

The leak is believed to have started on a site called Discord, a social media platform popular with people playing online games and where Teixeira is believed to have posted for years about guns, games and his favorite memes – and, according to some chatting with him, closely guarded U.S. secrets. Discord has said it was cooperating with the investigation.

In previous Associated Press stories, the leaker was identified as “the O.G.” by a member of the online chat group. Known as Thug Shaker Central, the group drew roughly two dozen enthusiasts who talked about their favorite types of guns and also shared memes and jokes, some of them racist. The group also held a running discussion on wars that included talk of Russia’s invasion of Ukraine.

In that discussion, “the O.G.” would for months post material that he said was classified – originally typing it out with his own notations, then a few months ago switching to posting images of folded-up papers because he felt his writings weren’t being taken seriously, said the member, who declined to share his name with AP.

It was not immediately clear how Teixeira would have had access to the records, but a Defense Department official told The Associated Press on Thursday that as an IT specialist responsible for military communications networks, the young Guardsman would have had a higher level of security clearance

Defense Secretary Lloyd Austin, in a statement issued after the arrest, said the Pentagon would conduct a review of its “intelligence access, accountability and control procedures” to prevent such a leak from happening again.