A Charleston-area man used encrypted web channels to get large amounts of potent drugs from Asia and Europe, then mailed orders to American customers, federal authorities said in court documents made public Wednesday.

Robert Bryan Mansfield, 60, of Pinewood Street in Ladson faces charges of conspiring to possess fentanyl with intent to distribute and conspiring to distribute the drug, a painkiller considered many times more potent than morphine. He appeared Wednesday in U.S. District Court in Charleston and is scheduled to have a preliminary hearing Friday.

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Robert Bryan Mansfield

Robert Bryan Mansfield. Cannon Detention Center/Provided

Mansfield's attorney, Dale Savage of Mount Pleasant, said Wednesday that he could not immediately comment on the case. Assistant U.S. Attorney Nick Bianchi is prosecuting Mansfield.

He was captured amid a Department of Homeland Security probe into an international drug-smuggling operation. Local police agencies, including sheriff's offices in Charleston and Dorchester counties, later got involved.

After his arrest, he told federal investigators how it worked, and the agents relayed portions of his account in an affidavit:

He used encrypted networks known as the "dark web" and anonymous Tor browsers to reach partners in China and Hong Kong. The drugs came via air courier from those countries, along with the Netherlands, Spain and Germany.

Between March 2016 and last month, nearly 7 pounds of fentanyl was sent to him.

His apartment housed a redistribution operation. Customers paid him through the virtual Bitcoin currency or Paypal. He then packed the drug and sent it away through the U.S. Postal Service.

One of his incoming shipments led to the effort's demise, a Charleston-based federal agent wrote in the affidavit, further describing how it played out:

The agent's New York counterparts responded Feb. 2 after more than 2 pounds of fentanyl was found in a shipping bag seized at John F. Kennedy International Airport's airmail facility. The drug was packed in a zipped plastic bag that was inside an airtight aluminum bag wrapped in bubble packaging.

The package had been sent from Hong Kong.

Local agents kept their eyes on Mansfield after that. One day last month, they watched him go to a Ladson post office and drop off a bag of mail. They intercepted the shipment of 12 packages that contained what appeared to be various drugs.

Authorities then searched his apartment on Friday, uncovering a large amount of narcotics, paraphernalia, scales, computers and shipping supplies. The loot included 3½ ounces of fentanyl, prompting a response from a hazardous-materials team and the evacuation of nearby homes.

On Wednesday afternoon, federal and local authorities served a search warrant at a storage unit at Public Storage, 3366 Ladson Road in Ladson, as part of the ongoing criminal investigation into Mansfield's operation, according to federal officials. 

Agents with the Department of Homeland Security, the Charleston County Sheriff's Office and the County's Hazardous Material Team participated in the search, said Maj. Eric Watson, a Sheriff's Office spokesman.

Officials did not immediately say what was found there.

Gregory Yee contributed to this report. 

Reach Andrew Knapp at 843-937-5414 or twitter.com/offlede.

Andrew Knapp is editor of the quick response team, which covers crime, courts and breaking news. He previously worked as a reporter and copy editor at Florida Today, Newsday and Bangor (Maine) Daily News. He enjoys golf, weather and fatherhood.