Boston―Jack Teixeira appeared in a federal district court Monday and pleaded guilty to the massive leak of U.S. intelligence documents last year on Discord, an online chat platform popular with video gamers.

Dressed in orange inmate fatigues and wearing a rosary, his ankles shackled, Teixeira stood before Judge Indira Talwani and acknowledged that the evidence would show he knowingly shared classified information on Discord with people who weren’t authorized to have it.

Teixeira made no formal statement and responded to the judge’s questions usually with a simple “Yes, your honor.”

Teixeira pleaded guilty to all six charges against him, including the willful retention and transmission of national defense information that the government had classified as top secret.

Teixeira was accused of using his top-secret security clearance to access classified government computer networks on an Air Force base in Cape Cod, where he worked with a unit providing intelligence support to the military. A Washington Post investigation revealed that, while Teixeira was serving in the Massachusetts Air National Guard, he shared hundreds of classified documents as well as his own summaries of classified reports on Discord.

In court, prosecutors explained that Teixeira would write down classified information inside the secure facility, then remove it and post the transcriptions to Discord under his handle TheExcaliburEffect. Audit data also showed that Teixeira accessed and printed hundreds of classified documents at the base, primarily using an isolated workstation in the basement of the intelligence facility, prosecutors said.

Teixeira had pleaded not guilty after his arrest last April. His lawyers spent the past several months reviewing the evidence, including classified documents, that prosecutors intended to use at trial.

“He is significantly remorseful for his conduct. He has accepted full responsibility for his conduct,” Teixeira’s attorney Michael K. Bachrach told reporters after the hearing. He said that Teixeira would address the court at a sentencing hearing in September. Teixeira has asked the judge to impose a sentence of 11 years.

But prosecutors are seeking a stiffer penalty of more than 16 years, which they argued reflected the severity of Teixeira’s crimes and would send a message to others who also took an oath not to disclose government secrets. The leaks were seen as one of the most serious breaches of U.S. national security in recent years. Some U.S. and European officials said the information could risk lives if it were widely known.

“Jack Teixeira will never get a sniff of a piece of classified information for the rest of his life,” Joshua S. Levy, the acting U.S. attorney for the District of Massachusetts, told reporters. “But we also bring these cases for general deterrence. The message goes out to anyone who may be tempted to violate their position of trust like Mr. Teixeira that there are very, very severe consequences.”

David Aaron, a former national security prosecutor who worked on leak cases, said the range of a potential prison sentence agreed upon by the two sides reflects the significance and potential harm of Teixeira’s disclosures - more egregious than of NSA contractor Reality Winner, who gave a single document to a news organization, but less harmful than CIA employee Joshua Schulte, who gave a raft of sensitive information to WikiLeaks.

“It really looks as though [Teixeira] was very cooperative early on, and the government gave him time to be cooperative, and that probably earned him substantial time off a sentence,” Aaron said. “That being said, he transmitted a lot of really sensitive stuff, and did it over a period of time.”

Teixeira had posted information about a vast range of topics, including the war in Ukraine, in a small Discord server called Thug Shaker Central that he formed with friends during the coronavirus pandemic. The group was united by a mutual interest in guns and military hardware, as well as a distrust of law enforcement agencies and embrace of racist and antisemitic views.

Teixeira also posted classified information about the war as early as February 2022 in another, larger server, called Abinavski’s Exclusion Zone, with hundreds of active users. The Post found that some of the members of the servers included foreign nationals, a fact that prosecutors have emphasized to show how Teixeira may have facilitated classified U.S. intelligence ending up in foreign hands.

“Mr. Teixeira enabled hundreds of members of his online chat groups, including individuals it was clear to him were located overseas, to further disseminate national defense information across the internet,” said Matthew Olsen, the assistant attorney general for national security.

As Teixeira awaited a possible trial, the tightknit members of Thug Shaker Central remained in touch on a new server, which included a channel devoted to updates on the case. At times, some users claimed the government’s case was weak, but they seemed not to appreciate the strength of the evidence.

On Monday, friends expressed a mixture of sympathy for Teixeira and frustration with the government’s insistence on a lengthy prison term.

“It’s cruel and unusual. Eleven to 16 years for exposing government secrets kept by taxpayer dollars just shows how the government is willing to silence you,” said a now 18-year-old former member of the server, who agreed to speak on the condition that he be identified only by his middle name, Charles.

“Jack Teixeira was and still is the best friend I have ever had. I regret absolutely nothing I’ve ever said or done with him,” Charles said.

“It was nice being able to read accurate info on the war, but was unsettling that he was so ready and willing to post it all,” said Jeremiah, a moderator on Abinavski’s Exclusion Zone who agreed to speak to The Post on Monday under the condition that only his first name be used.

It’s unclear whether investigators were able to fully re-create the extent of what Teixeira shared online. Before his arrest, Teixeira took advantage of Discord’s data retention policies to cover his tracks. He also deleted an entire server, called Thug Shaker Central, where The Post found that Teixeira had been sharing classified material with a group of mostly teenage boys in an attempt to impress them. Discord officials said Teixeira’s actions left them without an archive of the server to provide to law enforcement. A “thread” of messages containing information about the war in Ukraine also disappeared from another server where Teixeira was active, according to users.

Investigators first became aware of Teixeira’s actions early last year. On Feb. 28, 2023, a teenage member of Thug Shaker Central with the online handle “Lucca” began posting to a different server several dozen photographs of classified documents that Teixeira had taken. Five days later, yet another Discord user posted 10 of the photographs on Minecraft Earth Map, a server devoted to the popular video game. Soon the documents were swirling around the internet, and Pentagon and FBI officials scrambled to find their source.

After Teixeira’s arrest, authorities struggled to track the spread of classified material linked to him. The Post obtained more than 300 images showing classified documents as well as written posts containing additional intelligence that Teixeira’s friends said he had shared.

An Air Force Inspector General’s report cited lapses at the base where Teixeira worked, which would have made it easier for him to access classified material, including full-page printouts that he photographed and posted on Discord. During largely unsupervised night shifts, Teixeira and others were afforded “ample opportunity” to print material from the military’s classified networks, according to the report.