Ohio resident Larry Dean Harmon, 36, has been charged with laundering more than $300 million in bitcoin for darknet marketplace AlphaBay.

The man from Bath Township, about 30 miles south of Cleveland, was arrested Feb. 6 for conspiracy to commit money laundering, operating an unlicensed money transmitter business and money transmission without a license, according to cleveland.com. He is being prosecuted in the Northern District of Ohio.

Prosecutors said Harmon played a major role in scrambling illicit cryptocurrency transactions for AlphaBay. He is alleged to have run a mixing service called “Helix” that worked in conjunction with AlphaBay – one of the leading so-called “darknet marketplaces” accessible only via Tor browser. AlphaBay went offline in 2017.

Helix also worked with a handful of other marketplaces, the indictment said. It began operations in July 2014 and ran through December 2017.