ST. AUGUSTINE, Fla. -- An evidence technician with the St. Johns County Sheriff's Office was arrested early Wednesday after administrators said he admitted to taking up to $20,000 worth of confiscated prescription narcotics from the property room.

Paul Matthew Robinson, 38, was arrested at his home by investigators with the sheriff's office and the state attorney's office.

Robinson, who worked at the sheriff's office since 2001, was charged with grand theft an official misconduct and booked into the St. Johns County jail. His employment was terminated immediately.

According to officials, Robinson said he took the pills because he had chronic back pain. He also told investigators he acted alone.

"Anytime something like this happens in an agency is a shock," St. Johns County Sheriff's Office Sgt. Chuck Mulligan said.

Mulligan said Robinson is one of only a few people with access to the property room.

"Twenty-two years of being employed in the sheriff's office, I haven't been in that room," Mulligan said.

Authorities said the arrest was the result of an internal investigation that began when the evidence-room supervisor reported discrepancies in Robinson's paperwork.

When an audit of the property room determined that over 1,800 Loritab, percocet, OxyContin, Roxicodone and hydrocodone pills were missing, Sheriff David Shoar was notified. He immediately asked State Attorney R.J. Larizza and the Florida Department of Law Enforcement to conduct an independent criminal investigation.

The sheriff's office said a search of Robinson's home resulted in the seizure of several items, including evidence submission forms and other documents related to the missing narcotics.

"We will be conducting a thorough analysis of our protocols to enhance security to avoid an event like this from occurring again," Shoar said. "Whenever people are involved in a process there is always a risk of misfeasance, malfeasance, or criminal conduct, but it is even more troubling when that person has been entrusted by the public to perform a duty."

In addition to the criminal charges against one of their own, authorities are trying to determine if the theft of evidence could affect any pending criminal cases. A spokesman for the state attorney's office told Channel 4's Laura Mazzeo he believes the number of criminal cases involved is fewer than 10.