BOSTON >> Jack Teixeira, the Massachusetts Air National Guard member accused of leaking highly classified military documents on a social media platform, is expected to plead guilty in his federal case, according to court papers filed Thursday.

Prosecutors asked the judge to schedule a change of plea hearing for Monday, but no other details were immediately available. Teixeira had previously pleaded not guilty.

The Massachusetts U.S. attorney’s office declined further comment. An attorney for Teixeira didn’t immediately return a phone message Thursday.

Teixeira, of North Dighton, Massachusetts, has been behind bars since his April arrest for a leak that left the Biden administration scrambling to assess and contain the damage among the international community and reassure allies that its secrets are safe with the U.S.

Teixeira was indicted on six counts of willful retention and transmission of national defense information.

He was accused of sharing classified military documents about Russia’s war in Ukraine and other sensitive national security topics on Discord, a social media platform popular with people who play online games. Investigators believe he led a private chat group called Thug Shaker Central, where enthusiasts shared jokes, talked about their favorite types of guns and discussed wars, including Russia’s invasion of Ukraine.

Authorities say Teixeira, who enlisted in the Air National Guard in 2019, began around January sharing military secrets with other Discord users — first by typing out classified documents and then sharing photographs of files that bore SECRET and TOP SECRET markings. Teixeira worked as a “cyber transport systems specialist,” essentially an IT specialist responsible for military communications networks.

Authorities have said that Teixeira was detected on April 6 — the day The New York Times first published a story about the breach of documents — searching for the word “leak” in a classified system. The FBI says that was reason to believe Teixeira was trying to find information about the investigation into who was responsible for the leaks.

Billing records the FBI subsequently obtained from Discord helped lead investigators to Teixeira.

Prosecutors say he continued to leak government secrets even after he was warned by superiors about mishandling and improper viewing of classified information. After being admonished by superiors last year, he was again seen in February viewing information not related to the intelligence field, not his primary duty, according to internal Air National Guard memos filed in court.

Authorities have provided few details about an alleged possible motive, but accounts of those in the online private chat group where the documents were disclosed have depicted Teixeira as motivated more by bravado than ideology.

Prosecutors had urged the judge to keep Teixeira jailed while the case played, in part because of an arsenal of weapons found at his home and his history of disturbing online statements. They included one social media post from last November saying that, if he had his way, he would like to kill a “ton of people” because it would be “culling the weak minded.”

In pressing for their client to be freed from jail, Teixeira’s attorneys pointed to the pretrial release of former President Donald Trump and others in high-profile classified documents cases. Teixeira’s lawyers noted that prosecutors did not seek to detain Trump — or his co-defendant, Walt Nauta — even though they said the former president and his valet “possess extraordinary means to flee the United States.”

U.S. District Judge Indira Talwani last year denied Teixeira’s bid for release, saying “No set of release conditions will reasonably assure the safety of the community, or prevent destruction of evidence.”