09/04/2012 03:46 pm ET

Parents Bust Sex Offender On Facebook When He Refuses To Stop Dating Their Daughter (VIDEO)

How far would you go to protect your child? For Jesper and Julie Myrfors of Sedro-Wooley, Wash., keeping their teenage daughter out of harm's way meant participating in an elaborate Facebook hoax, one that Jezebel characterizes as "creepy." Their goal: to keep the 15-year-old from dating a registered sex offender.

The teenager started seeing William "Liam" Elms in April, the Skagit Valley Herald reports. A few months later, the Myrfors discovered that Elms was a registered level 1 sex offender under state supervision for a third-degree child molestation conviction. They told their daughter to stop seeing him, but the couple was unwilling to end their biweekly visits.

"We just thought she was getting into a dangerous situation,” the girl's father explained to King5.

Frustrated but undeterred, the parents decided to friend Elms on Facebook under the guise of a fictional 15-year-old girl named "Ashley Lynn Brooks," reports Q13 Fox. With help from one of their daughter's friends, the couple started an online back-and-forth with Elms, who believed his new Facebook crush "Ashley" needed to talk to someone about "problems with a friend."

"When we did this, we had rules," Jesper told King5. "We were not trying to entrap [Elms]. We were setting him up a situation where, if he was a bad guy, he could act on it."

And Elms didn't skip a beat. Soon after the online friendship began, he tried to convince "Ashley" to go camping with him and spoke openly about having sex with her. At that point, the girl's parents showed her what was going on.

"My daughter didn't know we had done this. I invited her on to begin watching live,” Julie told NBC News. "The hardest part as a parent was watching her heart break."

As soon as the conversation became "dirty, violent and nasty" -- Elms sent "Ashley" lewd pictures -- the concerned parents contacted police, Q13 Fox reports.

According to the Associated Press, police arrested Elms on August 18. He is likely to face charges of "immoral conduct with a minor" and is being held on $25,000 bail.