A former player for Washington’s pro football team pleaded guilty to federal charges that he conspired to defraud the Washington Metropolitan Area Transit Authority (WMATA) of more than $300,000, the U.S. Justice Department announced Friday.

Brian Carpenter, 59, who played in Washington in the 1980s, later owned a Leesburg-based company–The Flintstone Group–that sold janitorial products with names related to his NFL career, such as a cleaning product named “Blitz.”

According to court documents, Carpenter conspired with at least two Metro employees to charge company credit cards and appear as if they were buying cleaning supplies, which Carpenter never delivered. Carpenter kept the charged amount and paid the employees in cash for their role, according to a statement from U.S. Attorney G. Zachary Terwilliger.

Federal investigators found that Carpenter used the credit cards to process transactions with at least 10 different companies to give the impression that he ran a legitimate business. He then gave Metro fake invoices showing that the agency had paid for and received all of the products it ordered, the statement said.

In total, Metro spent at least $310,000 on products that were never delivered. Carpenter faces a maximum penalty of 20 years in prison when sentenced on December 15.

The Washington Post reported last year that WMATA’s inspector general began investigating the scheme more than five years ago, when the employees allegedly placed cleaning supplies in stations’ supply cabinets to appear as though the orders were legitimate.

“The blitz has been sniffed out, picked up and countered,” Terwilliger tweeted Friday.