Calling the case a “sad and serious breach of public trust,” a federal judge on Monday sentenced a former United States postal worker to six years in prison for stealing more than 6,000 credit cards from undelivered mail.

Chinh Vuong, 49, of Garden Grove was a processing clerk in Santa Ana for more than two decades before getting arrested in 2015 for stealing credit cards and selling them. His scam resulted in a loss of hundreds of thousands of dollars for Chase Bank and American Express, authorities said.

Vuong pleaded guilty in federal court last year to one count of conspiracy to commit bank fraud and one count of aggravated identity theft. He had faced up to 32 years in prison.

In his Monday sentencing, Judge Cormac Carney said the number of stolen credit cards was troubling.

“This wasn’t just a few cards that were taken,” he said. “This is a threat to the stability of our financial system.”

In addition to federal prison time, Vuong was ordered to pay about $295,000 in restitution to Chase and $30,000 to American Express.

Prosecutors said Vuong, a mail clerk since 1989, stole at least 6,240 credit cards in just one year by stuffing them into his waistband and carrying them out to his car on his breaks. Authorities said he targeted cards in envelopes that were marked as “underliverable.”

At least some of the thefts occurred while Chase was replacing old-style credit cards with chip cards, so there was a higher volume of cards being mailed out to people.

He would then sell the cards, offering, for example, 11 cards for $500, or 132 for $5,000, with his customers then making unauthorized purchases.

Prosecutors said he made at least $6,000 a month off of the scam, spending the funds on personal expenses such as designer handbags and boots and two BMWs.

In June 2015, he sold hundreds of cards to two law enforcement informants. Authorities then searched his Garden Grove home and seized 199 more stolen credit cards, and luxury items bought with the cards, including two dozen handbags by Prada, Louis Vuitton and Gucci and other brands.

Speaking before the judge on Monday, Vuong apologized and said he felt remorse for his “poor choices and stupid mistakes.”

Also speaking in court, a brother, Quan Vuong, asked the judge for leniency and said Vuong has already lost his savings and his retirement pension.

He said Vuong, who came from Vietnam as a refugee, has brought shame and embarrassment to his family.

“This country has been so good to us, and we are sorry to have let it down,” he said. “But we know he can change. He has changed for the better.”