The man arrested for allegedly leaking top secret U.S. military documents appeared in court for the first time on Friday after being charged with obtaining and leaking classified information.

Jack Teixeira, a 21-year-old member of the Massachusetts Air National Guard’s intelligence wing, is being accused of taking classified military documents and transmitting them online.

Evidence obtained in an investigation, including billing records, showed that Teixeira took at least one government document and posted it on an unidentified platform, according to charging documents. Discord, a messaging platform, has said it was cooperating with U.S. authorities after reports the documents were posted there.

Teixeira is facing up to 15 years in prison after being charged with violating 18 U.S.C. § 793 and 18 U.S.C. § 1924, which prohibit the unauthorized retention and transmission of national defense information and classified materials.

Teixeira was arrested outside a home in North Dighton, Massachusetts, on Thursday. He listed the home as his residence in military employment papers, according to the charging documents.

Teixeira appeared in court Friday in tan jail clothes for a brief proceeding at which U.S. Magistrate Judge David Hennesy, appointed by other judges, ordered him held pending an April 19 hearing.

Defense Secretary Lloyd Austin praised the Department of Justice and the FBI for its “swift arrest” in connection with the investigation into the leaks and said the Pentagon is still reviewing the implications of the unauthorized disclosures.

Austin said he was directing officials to review access to intelligence “to prevent this kind of incident from happening again.”

This is a developing story that will be updated.

The Associated Press contributed to this report.