Jack Techira, accused of leaking Pentagon documents, appeared Friday in federal court in Boston to face charges related to obtaining and disseminating national security information and keeping classified documents.
This comes as US President Joe Biden announced that he had ordered the intelligence community to "better secure" classified documents and information after the leak.
"As we continue to determine the credibility of these documents, I have ordered the military and intelligence agencies to take action to better secure sensitive information and limit its distribution," Biden said in a statement.
"Our national security team is coordinating closely with our partners and allies," he said, praising the "speed" with which security and judicial agencies acted following the leak of secret documents.
The FBI arrested Techira yesterday, and the US attorney general said that he works in the service of the National Guard, while US media reported that he is an information technology specialist.
The Pentagon spokesman said that the leaked documents are sensitive and that what happened was a deliberate crime, refusing to discuss the details of the leaked documents because of their sensitivity and impact on national security, allies and partners.
He said the Pentagon has strict rules for maintaining classified documents and that work is continuing with federal agencies to figure out the extent of the damage caused by the leak.
During his court appearance, Tichira was not asked to make any statements, and his detention is scheduled pending the second hearing scheduled for next Wednesday.
During the brief hearing in Boston, he was charged with charges including "storing and transmitting information related to national defense without authorization" and "withdrawing and storing confidential documents or materials without authorization," both of which carry prison terms of 10 and 5 years respectively.
During the hearing, his father shouted "We love you, Jack," and Techira replied, "I love you too, Dad."
The documents leaked by Techira revealed U.S. concerns about weaknesses in Ukraine's military and suggested the United States was spying on allied countries, including Israel and South Korea.
U.S. Attorney General Merrick Garland said prosecutors would seek "very severe punishments" for the defendant.
"People who sign agreements to access classified documents acknowledge how important it is not to disclose these documents to national security, and we intend to send a letter to show how important this is to our national security," he said.
Techira is suspected of publishing the documents as of early March in a private chat group on the social media platform Discord.
The New York Times reported that he was the director of the chat group called "Thag Shaiker Sinterll" and that he published the documents under the pseudonym "OJ."
The defendant initially shared with the group passages of classified documents, but later began posting photos of the documents asking the rest of the group not to share them, according to the Washington Post, but some of the documents appeared on other sites including Twitter, 4Chan and Telegram.