A Washington D.C. resident was sentenced to prison Tuesday for using fake names and local colluders to sneak heroin from Nigeria into the US capital region, while using the U.S. Postal Service as his unwitting courier.

Prosecutors say Steven Mason, 48, was part of a criminal ring that tapped sources of heroin and alprazolam — an anti-anxiety drug sold under the brand name Xanax — in African countries from 2014 to 2016 and then sold the drugs in Maryland and Northeast Washington, including the hip H Street corridor.

Washington Post reports that Mason and co-conspirator Andrea Miller, 49, who was sentenced in June, worked with a primary trafficker in Nigeria who would arrange to ship the drugs from places like Kenya, Tanzania and India, and list fake names as the recipients, according to the Office of the U.S. Attorney for the District of Columbia.

The heroin was hidden in other items, such as clothing, and sent through the U.S. mail.

Conspirators would wait for the heroin-filled packages to arrive at specific addresses, or get civilians to accept the parcels in exchange for cash or drugs.

Opioids such as heroin are killing tens of thousands of Americans each year, and cases like this one underscore the scourge in America.