A Virginia man convicted of turning his Chantilly medical clinic into “a haven for drug addicts” was sentenced to 15 years in prison Friday for illegally providing prescriptions for narcotic pain relievers to hundreds of people, at least four of whom died of overdoses in recent years, authorities said.

Paul Boccone, 56, who is not a trained medical professional, owned Chantilly Specialists, a pain-management clinic that became known among drug addicts as a place where they could buy prescriptions for powerful pain-relief pills, according to the U.S. attorney’s office in Alexandria.

Boccone, who was convicted of drug- and tax-related crimes in August, helped at least 600 people obtain more than 800,000 oxycodone-based pills, including an addict who got 14,400 pills in just 13 months, prosecutors said. Boccone was sentenced by Judge Claude M. Hilton in U.S. District Court in Alexandria.

An FBI agent wrote in a court filing that under Virginia law, a “non-physician medical provider” such as Boccone can write prescriptions under “a written agreement with a licensed physician who assumes responsibility.” The agent wrote that Boccone “would hire medical professionals with no background or specialized training in pain management” to help carry out the scheme.

One of those employees, Charles Brown, 52, a nurse-practitioner at Chantilly Specialists who had prescription-writing authority, was sentenced Friday to five years in prison for taking part in the conspiracy with Boccone.

“Customers would travel long distances — in some cases in excess of 350 miles, or over 12 hours round-trip — to be treated for reported severe pain” at the Chantilly clinic, according to the federal indictment of Boccone. Often more than 25 people a day would pay $200 or more apiece for “cursory examinations,” after which they would be given prescriptions for oxycodone-based painkillers.

“During one point in the conspiracy, egg timers were utilized to ensure that no patient was with a provider longer than 20 minutes,” the indictment says.