ST. JOHNS COUNTY, Fla. -- A 25-year-old Elkton man was arrested on sex charges after he and a teen were seen together in a bathroom stall of an area library, according to the St. Johns County Sheriff's Office.

Ryan Keith Hartley was charged on Monday with lewd or lascivious conduct upon a child and interference of custody.

According to the sheriff's office, the investigation began at the St. Johns County Library in Hastings at 5 p.m., when a library employee observed a man and a juvenile girl walking toward the bathroom together and another employee went to investigate.

As the library employee entered the women’s bathroom, she heard noises and observed the two in a stall with their pants around their ankles, according a report from SCSO.

"We have two librarians who witnessed a 25-year-old male and a 14-year-old female walk into a restroom together … obviously, they were very astute in realizing that was not appropriate and they followed the individuals in the restroom, where they found both individuals in a compromising situation," said Sgt. Chuck Mulligan.

The two were told to leave the library by another employee and complied.

A key, which is easily available to anyone at the library, is needed to get into the restroom and the couple had the key.

The county said it was investigating what happened in hopes of preventing future incidents.

"It's very unfortunate incident. We're very sorry that it has happened. We are going to be looking at measures to see how it was handled and to see what steps we can take to prevent future incidents like this," said St. Johns County spokeswoman Karen Pan.

The sheriff's office said its investigation revealed that the 14-year-old girl had left her home without her parents’ knowledge and met Hartley at the library.

She was later found with Hartley at a residence in the 10000 block of Gregory Avenue, according to deputies.

"We then went to a residence and found this young 14-year-old who was indeed a runaway at that point in time from her family's residence with the 25-year-old male," Mulligan said.

The girl was returned to her parents and the suspect was taken to into custody.

Hartley was booked into the county jail, where he remained in lieu of $250,000 bond following a first appearance hearing Tuesday morning.

The sheriff's office said Hartley has a lengthy criminal record but that no of criminal background has anything to do with children.