(CNN) — The 21-year-old Massachusetts man arrested by the FBI on Thursday in connection with the leaking of a trove of classified US government documents had a fascination with the military, guns and war, several former high school classmates told CNN.

Jack Teixeira was arrested in Massachusetts without incident, Attorney General Merrick Garland said. He made his initial appearance in US District Court in Boston on Friday morning and was charged with unauthorized retention and transmission of national defense information and unauthorized removal of classified information and defense materials.

Teixeira has a detention hearing scheduled for Wednesday and will remain detained until then. He did not enter a formal plea on Friday.

Teixeira would sometimes wear camouflage to school, carried a “dictionary-sized book on guns” and behaved in a way that made some students uneasy, former classmates said.

“A lot of people were wary of him,” said Brooke Cleathero, who attended middle school and high school with Teixeira. “He was more of a loner, and having a fascination with war and guns made him off-putting to a lot of people.”

John Powell, who also attended middle school and high school with Teixeira, said he recalled him as a pleasant and quiet kid who was sometimes picked on. “He didn’t have many friends,” Powell said.

Teixeira grew up in the suburbs of Providence, Rhode Island, according to public records. He attended Dighton-Rehoboth High School in Massachusetts where he graduated in 2020, according to the superintendent of the regional school district.

Powell recalled Teixeira occasionally toting around a textbook on military vehicles — tanks, planes and submarines — and having a fascination with anything “military-related” from an early age.

“He was dead set on joining some branch of the military, even as a kid,” Powell said.

Other students, who asked not to be identified, said they detected a more menacing vibe from Texeira, who some recalled making comments they perceived as racist or mumbling derogatory things about people under his breath.

One student recalled him showing up for school wearing a shirt with an AR-15 on it the day after the mass shooting in Las Vegas in 2017.

Teixeira didn’t behave in a manner that rose to the level where “people felt the need to report him,” another former classmate said, but “he made me nervous.”

The same student said she took his fascination with the military as a form of American nationalism and was therefore surprised by the allegations against him.

“I didn’t think he would be capable of doing something like this,” she said.

Worked in IT in Air National Guard

Teixeira was an Airman First Class in the Massachusetts Air National Guard, where he worked as a low-ranking IT official.

In his role as a Cyber Transport Systems journeyman, Teixeria would have been working on a network that carried highly classified information, according to a defense official, which is why he needed a security clearance.

He is believed to be the head of an obscure invite-only Discord chatroom called Thug Shaker Central, multiple US officials told CNN, where information from the classified documents was first posted months ago.

Teixeira has held a Top Secret clearance since 2021, according to the affidavit unsealed Friday. He also “maintained sensitive compartmented access (SCI) to other highly classified programs,” an affidavit says. Many of the leaked documents posted on the online server Discord were marked Top Secret.

At least one of the documents he allegedly posted was accessible to him by virtue of his employment with the Air National Guard, the affidavit says.

According to a Discord user interviewed by the FBI, Teixeira began posting information in December 2022, according to the affidavit, and began posting photos of documents around January 2023.

This story has been updated with additional reporting and developments.

Man arrested in connection with intel leak was a loner who was fascinated by war and weapons, former classmates say