A man who said he’s “guilty as sin” of holding up a Kauai pharmacy with a BB gun employees believed was a real firearm was sentenced Tuesday to about six years in federal prison.

“Normal people don’t get up in the morning and decide to rob a pharmacy,” Walter Mills said at his sentencing hearing in federal court in Honolulu. “There’s clearly something wrong with me.”

He has severe drug addiction and mental health issues, said his defense attorney, Clarence McCurdy Virtue.

Mills, 42, previously pleaded guilty to robbing Kapaa Pharmacy last year. According to a plea agreement, he wore a mask and carried a BB gun, which he pointed at employees. He stole nearly 2,000 pills of OxyContin, oxycodone, hydrocodone, morphine and methadone, the court document said.

The robbery traumatized employees who “had no idea the gun he had was not a real gun,” Assistant U.S. Attorney Jill Otake said. She noted Mills is facing sentencing in state court for a separate Walmart theft case.

Mills said he considers himself a nonviolent person, yet acknowledged he traumatized people. “I don’t feel good about that,” he said. “What happened was bad. … I’m guilty as sin.”

It’s understandable that seeing a masked Mills racking the slide on the BB gun made the employees fearful, U.S. District Judge Derrick Watson said. At least one of the two employees has since quit, he said.

But Mills quickly took responsibility, Watson said. “It really is uncommon for someone to be so perceptive of what they’ve done,” he said.

In addition to the 70 months of imprisonment, Watson also sentenced Mills to three years of supervised release, with conditions including drug testing. Mills must also pay back $1,073.42 for the value of the pills.