A couple in Idaho who called the FBI regarding the disappearance of Colorado mom Kelsey Berreth have revealed more about their impressions of Patrick Frazee and the Twin Falls nurse who is reportedly being investigated for a possible role in Berreth’s presumed murder.

Patty and Joe Rockstahl have given a lengthy interview to CBS, which has been published in segments. As CrimeOnline previously reported, the Rockstahls said they became connected to the case after one of their employees came to them in October and said her best friend, Krystal Lee, has been asked by a man she knew to kill the mother of his child. The couple said that initially, they didn’t think they had enough information to take to the police, but Patty Rocktstahl changed her mind after she saw Kelsey’s mother Cheryl Berreth plead for her daughter’s return on television. The Rockstahls contacted authorities, and learned by that time that the FBI was already in the area.

Although the Rockstahls did not personally know Lee, at least as of October, they appear to have gleaned a lot of information about her relationship with Frazee.

“She was in love with him from a very young age,” Patty Rockstahl told CBS News.

“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.”

The Rockstahls claimed that Lee and Frazee became involved right after high school, though Lee went on to marry and divorce someone else. She now has two children.

The couple believes that Frazee asked Lee three times to murder Berreth, and also asked her to help dispose potential evidence, allegedly threatening her.

“Patrick told Krystal that little girls go missing off the playground all the time,” Patty told CBS News.

“Krystal was so scared, he was so angry that he said things that made Krystal think he had killed before,” Joe said.

The Rockstahls did not specify what had let Lee to believe Frazee may have previously killed anyone. The interview also does not specify the nature of their business and the work of the employee who is Lee’s friend. The results of online searches indicate that Joe Rockstahl is a personal injury attorney with his own firm.

The couple said they believe Lee had been to Colorado as recently as November. Patty Rockstahl also offered a theory about a motive, claiming that Frazee “felt that Kelsey was going to harm the child, that she was crazy.”

Berreth went missing on November 22, Thanksgiving Day. Patrick Frazee has been charged with multiple counts of murder and solicitation of first-degree murder, although Berreth’s body has not yet been found.

CBS News is expected to publish another segment of the interview this weekend.