A South Carolina sheriff's deputy was arrested for allegedly arranging to meet with an underage girl for sex in an undercover operation ⁠— a sting set up by his own department.

Derek Vandenham, a former deputy with Richland County Sheriff's Department, was one of several people arrested last week following a five-day sting to catch predators who use social media and online chat rooms to arrange to meet up with minors or prostitutes for sex, Sheriff Leon Lott said at a news conference on Tuesday.

Lott said Vandenham was "working, on duty, in my car, in my uniform ... and was communicating to have sex with a 15-year-old." He was charged with soliciting a minor and attempted criminal sexual conduct with a minor.

Vandenham, 34, was immediately fired upon his arrest last Tuesday, Lott said. He had been with the department since August 2015.

"One of the most disgusting things that I've been having to deal with is to have a deputy do something like this," Lott told reporters.

In a statement to NBC News, Lott said he would recommend that Vandenham's "certification be revoked so he never works in law enforcement again.”

Five people, including Vandenham, were arrested after traveling to an arranged meeting spot. Nine others have warrants out for their arrests.

They all thought they were communicating with girls as young as 13, Lott said, calling them "monsters."

According to Lott, some of those arrested traveled from as far as Florida and Georgia.

"Unfortunately, some of them we work with, like a deputy sheriff at Richland County Sheriff's Department, some of them we go to church with," he said. "But we've got monsters that live in our community and they prey on our children and our job is to protect our children."

The sting, which involved multiple law enforcement agencies, also led to the arrest of former South Carolina transportation commissioner John Hardee, who allegedly arranged a meeting with an undercover agent to have sex with an adult prostitute, Lott said.

Hardee was one of 14 "johns" arrested in the sting.

A spokesperson for the Transportation Commission said it "has no comment at the present time," but said Hardee was "removed" from the Commission long before his arrest.