(CBS) — A couple in Idaho claims to have new details in the disappearance of Colorado mother Kelsey Berreth — including an alleged affair and possible murder plot involving Berreth’s fiancé, Patrick Frazee. Patty and Joe Rockstahl claim they learned the information from one of their employees, a close friend of allegedly had a relationship with Frazee.
The Rockstahls told CBS News correspondent Nikki Battiste their employee told them Lee and Frazee first began a relationship just after high school.
“She was in love with him from a very young age,” Patty Rockstahl said, adding, “She was very vulnerable and I think she cared for him, and he took advantage of that… He was her first love, I understand, and… he had a hold on her.”
A source tells CBS News the FBI questioned Lee regarding her possible role in Berreth’s disappearance and tells us she is cooperating.
The Rockstahls said they were told Lee, a nurse from Idaho and a mother, visited Frazee as recently as November – the month Berreth vanished.
Frazee iseven though her body hasn’t been found.
Berreth disappeared from her Woodland Park home on Thanksgiving, after dropping off their 1-year-old daughter with Frazee.
The Rockstahls claim their employee said Frazee threatened Lee, and she may have helped him dispose of evidence.
“Patrick told Krystal that little girls go missing off the playground all the time,” Patty Rockstahl said.
“Krystal was so scared, he was so angry that he said things that made Krystal think he had killed before. So of course, she’s going to be terrified,” Joe Rockstahl said.
The Rockstahls said they were told Frazee asked Lee three times as early as October to help kill Berreth, the mother of his child, but Lee refused.
Asked what they heard was Frazee’s motive, Patty said, “That he felt that Kelsey was going to harm the child, that she was crazy.”
“Is Krystal Lee a murderer?” Battiste asked.
“I don’t believe so. I don’t,” Patty Rockstahl said.
Berreth was last seen on a surveillance video at a Safeway in Woodland Park on Thanksgiving Day with her and Frazee’s 1-year-old daughter.
Three days later, police said Berreth’sin Gooding, Idaho. Several texts from the phone were sent including one to her employer saying she would be away for a week and another to Frazee. Patty said she thinks Lee sent the texts.
“She had the phone,” Patty said. “She was probably instructed to send those texts by Patrick but that’s – there’s nobody else that could’ve sent those texts to my knowledge.”
“Why would Krystal Lee, a nurse with children, help Patrick Frazee cover up the murder of his fiancée?” Battiste asked.
“I think she was afraid and I think she got in over her head,” Patty said. “She was in love with Patrick and we’ve all heard the stories of what people will do for love.”
The Rockstahls have never met Lee in person. Lee has not been charged with any crime related to Berreth’s disappearance.
Frazee has been charged with two counts of first-degree murder and three counts of solicitation to commit murder in the first degree, according to District Attorney Dan May. The charges reflect prosecutors’ dual theories of the crime.
Authorities have searched Frazee’s property in Florissant and their search there involved heavy digging equipment.
A jury trial for one of the two wrongful death suits Frazee is facing is scheduled to begin next month.