A 21-year-old Massachusetts Air National Guardsman, Jack Douglas Teixeira, faced a federal judge in Boston on Friday, accused of unlawfully removing and retaining classified military intelligence records.
Teixeira was arrested by the FBI at his North Dighton residence on Thursday.
During his initial court appearance, he wore a brown khaki jumpsuit.
Boston’s top federal national security prosecutor, Nadine Pellegrini, requested that Teixeira be detained pending trial.
A detention hearing was scheduled for Wednesday.
The classified documents at the center of the investigation were posted on a social media platform in March, but they only gained attention after the New York Times reported on them last week.
The leak is considered the most severe security breach since WikiLeaks published more than 700,000 documents, videos, and diplomatic cables in 2010.
U.S. officials continue to assess the damage caused by the leaks, which disclosed alleged details of Ukrainian military vulnerabilities and information about allies, including Israel, South Korea, and Turkey.
Teixeira spoke only twice during the brief proceeding, answering “yes” when asked if he understood his right to remain silent, according to a report from Reuters, which also explained the national guard member confirmed that he had completed a financial affidavit, permitting him representation by a federal public defender.
Convictions for willful transmission of national defense information carry a maximum sentence of 10 years in prison. However, depending on the charges brought against him, Teixeira could potentially face a longer sentence.
Billing records from an Internet social media platform helped the FBI identify Teixeira as the suspect in the leak, according to unsealed court records, The Associated Press (AP) reports.
It is believed Teixeira shared the documents, which have not been authenticated individually by U.S. officials, in an online private chat group he led on the social media platform Discord.
The classified documents cover topics related to briefing slides mapping out Ukrainian military positions, assessments of international support for Ukraine, and scenarios in which Russian President Vladimir Putin might use nuclear weapons.
The documents apparently revealed that mainstream media sources and the U.S. government under President Joe Biden are misinforming the public by significantly overreporting Russian military casualties.
The documents also showed that the U.S. does in fact have military personnel on the ground in Ukraine, despite Biden’s claims otherwise.