The scheme unraveled after a customer noticed that a U.S. Treasury check he was supposed to receive had been stolen and deposited in the name of his mail carrier.

Ninety out of the 98 stolen checks were U.S. Treasury checks, many of them worth tens of thousands of dollars, prosecutors said. He deposited one U.S. Treasury check worth $415,173.53, records show.

Lewis, who was a postal worker, was allegedly recruited by Williams to steal and sell him valuable business checks. The stolen checks equaled over $17 million and Williams sold them to other scammers through a Telegram channel.