A retired Air Force sergeant swiped credit and debit cards from fellow service members, often as the victims exercised at base gyms, according to a federal grand jury indictment.

Former Senior Master Sergeant Christopher Dwan Underwood, 42, was arrested Friday after he used his retiree status to gain access to gyms on San Diego-area military bases.

There, he preyed on his fellow service members who left their personal belongings behind as they worked out, the indictment claims.

More the 30 times, Underwood swiped military-issued credit, debit cards and the service members’ birth dates and social security numbers, the indictment says. That included victims’ government travel charge cards, which can only be used when the cardholder is on official military travel.

The court document alleges Underwood called Citibank to activate the cards, using the service members’ person information.

He is accused of making more than $20,000 worth of unauthorized purchases and cash advances.

Appearing before a federal judge Monday, Underwood was charged with wire fraud, bank fraud and aggravated identity theft.

He is scheduled to be back in court for a bond hearing on July 3.