On Wednesday, a former NSA contractor was indicted by a grand federal jury on charges he willfully retained national defense information.

US government officials claim the incident could be possibly the largest government seizure of stolen information in history.

Facing 20 criminal counts each amounting to 10 years maximum in prison is former employee Harold Thomas Martin, 52, the justice department said.

The accusation reads that Martin stole highly classified government data from the U.S. intelligence community over a period of up to 20 years. The information was related to national defense and was hoarded at his home in Glen Burnie, Maryland.

Martin’s first appearance with the U.S. District Court of Baltimore is scheduled for Tuesday, acording to the Justice Department.