Parker-- Investigators arrested 18-year old Stephanie Pistey Monday, charging her with accessory to murder and giving false information in a missing person investigation.

Pistey claimed Hendershot raped her, which investigators believe was the motive for the murder. Pistey's boyfriend, 17-year-old William Henry Chase, along with 25-year-old Joel Millsap and 20-year-old James Gay allegedly lured Hendershot to a house, where they beat him to death.

Chase and Millsap are charged with murder and Gay's charged with aggravated battery. It was Chase and Pistey who gave police the information they needed to find Hendershot's body.

After the beating, police say the suspects dumped Hendershot's body down a storm drain in some woods near the DuPont Bridge.

Chase supposedly admitted he and Millsap stripped-off Hendershot's clothes, stole a boat, then threw his clothes along with their own, into East Bay.

Investigators say Pistey was there during the murder and helped cover it up. They say her postings on Facebook helped give them the evidence they needed to arrest her.

"Originally she was the focus on the investigation, part of the focus of the investigation. But further leads from things that had been posted onto various social networking sites lead us into some other areas that actually helped us with the investigation," said Parker Police Chief, Charles Sweatt.

Pistey is due in court Tuesday morning for a bond hearing. Sweatt says as many as 7 people knew about Hendershot's murder, but never said anything. He says he expects to make more arrests.