Police say 53-year-old John Kochis was involved in a billing dispute with a Texas based department store chain last year.
His bill was mailed to the home office in November with the words, "Beware: Anthrax" written on the envelope.
Police say tests on the letter and its contents came back negative. But authorities initially treated the case as anything but a hoax.
Police say Kochis could have been charged with a federal offense. He faces up to 10 years in prison if he's convicted.