WASHINGTON (Nexstar) — The 21-year-old Air National Guardsman accused of stealing and leaking Pentagon documents appeared in court Friday.

According to court documents, authorities were able to track down the suspect through billing records of the social media platform he was using.

Jack Teixeira, 21, faces charges under the Espionage Act.

“There are very serious penalties associated with that,” U.S. Attorney General Merrick Garland said.

Authorities say Teixeira was the leader of the private chat group where the military documents were first leaked in December. The Justice Department says it will seek the most serious consequences.

“We intend to send that message, how important it is to our national security,” Garland furthered.

Court documents reveal that before his arrest, Teixeira tried to find out if authorities were on to him by searching the word “leak” in a classified system.

“This individual and any of his accomplices need to be prosecuted to the fullest extent of the law. They betrayed the confidence of their country,” Rep. Jake Auchincloss (D-MA) said.

The Massachusetts congressman says besides holding the leaker accountable, the Pentagon needs to answer some serious questions “about why it is that a junior-enlisted Air National Guardsman has need-to-know access to highly sensitive document information about Ukrainian war plans.”

Democratic Rhode Island Senator Jack Reed says he expects a review of how someone gains security clearance.

“What is hard to capture is someone who either later changes their mind about the importance of secrecy, or someone who’s deliberately concealing information,” Sen. Reed said.

The judge in the case ordered Teixeira to remain in custody until his next hearing on Wednesday.