A Massachusetts Air National Guard member charged with leaking highly classified military documents will remain behind bars while he awaits trial, a federal magistrate judge ruled Friday.

The ruling comes after prosecutors revealed that 21-year-old Jack Teixeira had a history of violent rhetoric, and was caught by superiors months before his arrest taking notes on classified information or viewing intelligence not related to his job.

In ordering Teixeira to remain locked up, U.S. Magistrate Judge David Hennessy cited his “fascination with guns,” disturbing online statements and prior admonitions by superiors about his handling of sensitive information. He said the criminal case represented “a profound breach of the defendant’s word that he would protect information related to the security of the United States.”

“Who did he put at risk? I mean, you could make a list as long as a phone book,” Hennessy said, including military personnel, medical workers overseas and Ukrainian citizens.

The judge also indicated that he found persuasive prosecutors’ arguments that U.S. adversaries who might be interested in mining Teixeira for information could facilitate his escape.

“It doesn’t seem implausible at all that a foreign government would make an overture to this defendant to get information,” Hennessy said.

Teixeira has been behind bars since his April 13 arrest on charges, under the Espionage Act, of unauthorized retention and transmission of classified national defense information. He has not yet entered a plea.

Prosecutors had urged the judge to keep Teixeira jailed, in part because of his arsenal of weapons and history of online statements, including 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.”

His lawyers had pressed the judge to release him to his father, saying he has no criminal history and strong family support to ensure he shows up in court. His lawyer said last month that he has “nowhere to flee” and “will answer the charges” against him.

Teixeira is accused of sharing classified military documents on Discord, a social media platform popular with people playing online games. The stunning breach exposed to the world unvarnished secret assessments on Russia’s war in Ukraine, the capabilities and geopolitical interests of other nations and other national security issues.

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

In court papers urging the judge to keep him in custody, prosecutors detailed a troubling history going back to high school, where Teixeira was suspended in 2018 when a classmate overheard him discussing Molotov cocktails and other weapons as well as racial threats. His initial application for a firearms identification card that same year was denied due to police concerns over those remarks.

He regularly made statements about violence and murder on social media, and also used his government computer to research past mass shootings and standoffs with federal agents, according to prosecutors.

Prosecutors said he also kept his gun locker within reach of his bed and in it were handguns, bolt-action rifles, shotguns, an AK-style high-capacity weapon and a gas mask.

Teixeira’s father told the judge that he removed all the guns from his home and would ensure that his son followed his pretrial conditions if he were released. Teixeira’s lawyer argued that despite the statements highlighted by prosecutors he was not a danger to the community or a flight risk.

“You have a young man before you who didn’t flee, has nowhere to flee,” defense attorney Brendan Kelley told the judge at his detention hearing.

Prosecutors said in court papers filed this week that Teixeira’s superiors had raised concerns in the months before his arrest about his mishandling of classified information.

He was twice admonished by superiors in September and October, and was again observed in February viewing information “that was not related to his primary duty and was related to the intelligence field,” according to internal Air National Guard memos filed in court.

The revelations have raised questions about why Teixeira continued to have access to military secrets after what prosecutors described as “concerning actions” related to his handling of classified information.

The high-profile case is being prosecuted by the Massachusetts U.S. Attorney’s office, whose leader — U.S. Attorney Rachael Rollins — is expected to resign by the end of the day Friday after two federal watchdog agencies found she committed a slew of ethical and legal violations.