But the low-ranking national guardsman who possessed top secret security clearance at a young age is accused of being just that, and faces years in prison if convicted of leaking dozens of classified documents.

The portrait painted in the US media by people who know Teixeira is more one of a naive young man seeking to impress friends than a crusading whistleblower intent on blowing open American secrets.

The 21-year-old from the small town of Dighton in southern Massachusetts enlisted with the US Air Force National Guard in September 2019.

According to court documents citing government records, Teixeira reached the rank of airman first class -- the third-lowest for enlisted air force personnel -- in May 2022.

He is a communications and IT specialist based at Otis Air National Guard Base in Cape Cod, around 70 miles (110 kilometers) south of Boston.

As of February this year, Teixeira's title was cyber defense operations journeyman, an FBI agent said in a court affidavit released Friday.

Special Agent Patrick Lueckenhoff added that, "As required for this position, Teixeira holds a top secret security clearance, which was granted in 2021."

In addition to that clearance, Teixeira also maintained "sensitive compartmented access (SCI) to other highly classified programs," since 2021, Lueckenhoff added.

SCI is information that is further restricted. To receive access, Teixeira would had to have agreed to "properly protect" the information by not disclosing it to people without privileged access.

He would also have been required to agree not to remove it from "authorized storage facilities" or hold it in "unauthorized locations," the affidavit added.

The criminal complaint alleges that Teixeira began posting classified information in a chat group on the internet platform Discord in and around December last year.

The group's purpose was "to discuss geopolitical affairs and current and historical wars."

Teixeira is accused of first posting paragraphs of text from documents before going on to post photographs of the documents themselves.

- 'Loner' -

The government says computer logs show that Teixeira accessed a document about troop movements in the Russia-Ukraine war a day before it was reposted online.

One friend told the paper that Teixeira had not wanted to undermine US national security but hoped to educate younger members of the online group.

"He loved America but simply didn't feel confident in its future," the Post quoted the person as saying.

Other members of the group said Teixeira had shared racist and anti-Semitic jokes.

Teixeira comes from a family with decades of military service, according to the Washington Post.

His stepfather spent 34 years in the same unit as his son, while Teixeira's mother worked for non-profit organizations that support veterans, the newspaper said.

Friends told the Post that Teixeira was patriotic, a devout Catholic and a libertarian. They added that he had an interest in guns.

Former classmates told CNN that he would sometimes wear camouflage to school.

"He was more of a loner, and having a fascination with war and guns made him off-putting to a lot of people," said one.