WASHINGTON – A former National Security Agency computer developer was sentenced Tuesday to five and a half years in prison after pleading guilty to storing troves of classified documents at his home.

Nghia Hoang Pho, 68, of Ellicott City, Maryland, had pleaded guilty to willful retention of classified national defense information.

From 2010 through March 2015, Pho removed top secret and what is called sensitive compartmented information about national defense and stored the material in a number of locations around his home, according to the plea agreement. Pho knew that he wasn’t authorized to remove the material from work or store it at home, according to the agreement.

U.S. District Judge George Russell issued the sentence that also carried three years of supervised release.

“Pho’s intentional, reckless and illegal retention of highly classified information over the course of almost five years placed at risk our intelligence community’s capabilities and methods, rendering some of them unusable,” said John Demers, assistant attorney general for national security. “Today’s sentence reaffirms the expectations that the government places on those who have sworn to safeguard our nation’s secrets.”

Pho, a naturalized U.S. citizen originally from Vietnam, began working at NSA’s Tailored Access Operations in April 2006 and held a variety of security clearances. Tailored Access Operations collected intelligence from foreign information systems and took actions to prevent, detect and respond to unauthorized activity within Defense Department computers.

Over his years of holding a security clearance, Pho received training regarding the proper handling, marking, transportation and storage of classified information, prosecutors said. Pho was also told that unauthorized removal of classified materials, and the transportation and storage of those materials in unauthorized locations, risked disclosure of the materials and could endanger national security.

“Removing and retaining such highly classified material displays a total disregard of Pho’s oath and promise to protect our nation’s national security,” U.S. Attorney Robert Hur said. “As a result of his actions, Pho compromised some of our country’s most closely held types of intelligence, and forced NSA to abandon important initiatives to protect itself and its operational capabilities, at great economic and operational cost.”