Oftentimes, walking into a Starbucks is more like walking a community office space than a coffee shop. But while it’s almost expected that people conducting job interviews or writing their latest magazine story will turn Starbucks into their office, would you ever expect a Starbucks to become a doctor’s office? One Orange County, Calif. doctor did exactly that, and was recently sentenced to 11 years in prison for illegally prescribing medications.

Dr. Alvin Yee, 44, pleaded guilty to seven counts of illegal distribution of a controlled substance by a practitioner last month, and was recently sentenced to 11 years in federal prison. The controlled substances include the powerful opioids OxyContin (oxycodone) and Vicodin (hydrocodone), and the anxiety medication Xanax (alprazolam).

The illegal activity was discovered through an investigation by the U.S. Drug Enforcement Administration (DEA), which found that Yee was selling prescriptions for the drugs out of a Starbucks in order to finance his eventual private practice. One-third of his Starbucks clients were ages 25 and younger, and the drugs they obtained through his prescriptions led to two of their deaths.

“The defendant consciously disregarded … the consequences of improperly prescribing narcotic drugs for greed,” court documents said, according to KTLA.

Yee told ABC’s 20/20 that starting in 2010, he began saving for his own private practice. He would go to Starbucks and perform examinations, using his stethoscope to listen to patients’ hearts, lungs, and to monitor vital signs. Soon after, he realized that he needed more money, and began seeing patients in need of pain medication. Derek Rosas, a former lacrosse player, who was still having pain from an injury was one of Yee’s patients, and subsequently died from his addiction to OxyContin.

Yee’s pain management eventually turned into more of a drug dealership as his so-called patients began to show up with anywhere from $300 to $600 in exchange for up to three-month’s worth of prescription medications.

The DEA eventually caught on to Yee’s activity, and during an eight-month investigation, they sent two undercover detectives to obtain prescriptions. The first detective told Yee that she was there for her friend in order to pick up prescriptions for OxyContin and Xanax. Yee handed her the prescription and told her to keep the illegal transaction quiet. The second detective told Yee that she was a recovering heroin addict — heroin is also an opioid — and that she was even borrowing painkillers from a friend. “You won’t be having to bum off of your friends anymore,” Yee responded, according to 20/20.

Although Yee had moved into his own office by Sept. 2011, the DEA already had enough evidence to charge him, and did so on 56 counts of prescribing controlled substances without a legitimate medical purpose. When asked about his 11-year sentence, he told 20/20, “I’ll take responsibility for… lapses in judgment. You know … everybody makes mistakes, but I never really felt that through all the people that I did help, that I would end up completely losing everything most dear to me.”

Every day, 105 Americans die from a prescription drug overdose, while another 6,748 people are treated in emergency rooms for prescription drug-related illnesses, according to the Centers for Disease Control and Prevention (CDC). Abuse of prescription painkiller has also risen in recent decades. In 2002, retail pharmacies filled more than 174 million prescriptions for opioid painkillers, compared to 256 million in 2009. A recent study found that these rates could have risen because of greater access to healthcare.