Sources who claim to have knowledge of accused murdered Patrick Frazee’s relationship with an Idaho nurse reportedly under investigation for allegedly helping dispose of missing Colorado mother Kelsey Berreth’s body have said they believe Frazee had a “hold” on Krystal Lee.

Joe and Patty Rockstahl have spoken to KMTV about the Kelsey Berreth murder investigation, claiming that one of their employees is the best friend of a woman believed to have been involved with Frazee, and who may have had some role in Berreth’s disappearance.

The pilot and mother of a one-year-old daughter went missing on Thanksgiving Day. Frazee has been arrested and charged with multiple counts of murder, though authorities have not yet found Berreth’s body.

The Rockstahls claimed their employee came to them in October and said that a man had asked her best friend, Lee, to murder or help murder the mother of his child, believed to be Berreth. The couple did not contact authorities about this allegation until after Berreth disappeared and Patty Rockstahl saw Kelsey’s mother Cheryl Berreth on television, putting together that Berreth was likely the woman connected to the story her employee had shared.

Since then, the couple has apparently learned from Lee’s friend that the registered nurse went to visit Frazee in Colorado as recently as November, but tried to talk her out of it.

“She was concerned about Krystal,” Patty Rockstahl said of the friend. “She was very concerned that she was going to meet someone that had asked her to murder someone.”

Patty also told the news station that Krystal Lee has known Patrick Frazee since she was 18, and that they may have even owned horses together. The precise nature of the relationship between Frazee and Lee, a divorced mother of two, is unclear, though Patty Rockstahl claims Frazee has a “hold” on Lee.

Authorities have not identified any additional suspects since arresting Frazee on December 21, but authorities have indicated that more suspects will be identified.