FARGO — Just days before her death in October 2015, Amanda Stach Engst sent out a series of text messages, saying "they" were driving to "the rez" and she was afraid "he" would hurt her.

"If you don’t hear from me tomorrow, then something went wrong. … But you know what I drive and 'they' are Billy and Crystal Herman," one text from the 36-year-old woman said.

Four months later, Engst’s body was found Feb. 4, 2016, in the Sheyenne River on the Spirit Lake Indian Reservation south of Warwick, N.D. Prosecutors allege Billy Joe Herman, 40, strangled Engst from behind with a cord while his then-wife, 40-year-old Crystal Marie Herman who's now known as Crystal Johnson, drove Engst’s vehicle in mid-October 2015.

He beat Engst with a shovel before putting her body in the river, according to court documents and transcripts from hearings leading up to Johnson’s 2018 sentencing in Eddy County District Court. Johnson was ordered to serve 20 years in prison after pleading guilty to a Class AA felony of accomplice to murder.

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Herman has pleaded guilty to second-degree murder in U.S. District Court, and prosecutors will ask that he serve life in prison without parole when he is sentenced Friday, Oct. 18, in Fargo.

Federal prosecutors and investigators have shared few details in the case, but transcripts from Johnson’s hearings, divorce filings and other court documents shed light on what brought Herman, Johnson and Engst together, including claims that Herman would harm his and Johnson's child if Johnson didn’t go with him in the weeks leading up to Engst’s death.

The documents and transcripts also describe Engst’s messages of concern for her safety, what unfolded the night she died and evidence linking the couple to the killing amid an investigation into their robbery spree in the Red River Valley.

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'Can't talk now'

Herman and Johnson had a child together in 2010 before they were married in 2011 in Warwick, according to divorce filings in Clay County District Court.

Johnson filed for divorce in early September 2017, and it was finalized in April 2018, along with Johnson’s name change.

Former Eddy County State’s Attorney Travis Peterson read aloud facts of the case during Johnson’s change of plea and sentencing hearings. He said Herman and Johnson were separated but still married in September 2015, when Herman arrived at Johnson’s mother’s house and told Johnson to come outside.

“According to Crystal, Billy Herman demanded that Crystal come with him, and that if she didn’t, he would harm their child,” Peterson said, according to the transcript. “So needless to say, Crystal Herman went with Billy Herman.”

Billy Herman’s criminal history before Engst’s murder included several assaults, domestic violence and disorderly conduct. Johnson’s criminal history involved writing bad checks, theft and child neglect, according to Peterson.

Peterson did not return messages left by The Forum of Fargo-Moorhead. The newspaper also contacted the law firm of Johnson’s defense attorney, which declined to comment.

The couple traveled around the Red River Valley and the Devils Lake area “never staying very long in one place,” according to the transcript. Investigators believe there was “illicit drug use and association with” dealers and users, Peterson told the court.

Herman “became acquainted with” Engst in the summer of 2015, but it appears Johnson did not know Engst before the fall of 2015, the transcript said.

Engst was originally from Breckenridge, Minn., but she lived in different towns before coming to Warwick, N.D., her last known location, according to authorities.

She lived with her aunt, Jamie Anderson of Halstad, Minn., for a time. Anderson previously told the Forum News Service that Engst was a “wild child, but she was very caring and wanted to help.”

"She would do anything for her family and was always there,” Anderson said. Engst had three children of her own.

The last time Engst contacted Anderson was via Facebook on Oct. 12, 2015, the day before she died.

"There's stuff going on," Anderson said Engst wrote in the message. "I can't talk now. I'll call you when I can."

Driving to the bridge

Engst used her 1997 Oldsmobile Cutlass to travel with Herman and Johnson, the transcript said. Law enforcement described text messages that showed Engst’s concern for her safety.

They noted Oct. 7 and 8 messages to Herman’s nephew, in which Engst said Herman was “freaking out” and talking about wanting to kill himself.

One message said she was scared “he will hurt me, since I was told that they are going to the rez and I’m not sure why.”

“He won’t give me my keys and the title he has for my car,” another message said.

Herman, Johnson and Engst were at Wood Lake in Benson County, where investigators believe “there were some drugs and alcohol involved,” the transcript said.

According to Peterson:

Herman strangled Engst on the Spirit Lake Indian Reservation, and Johnson reached across Engst to open the passenger door, letting the victim fall out. Johnson then moved items around to make room for Herman to put Engst in the trunk.

Herman then drove Engst’s vehicle about 6 miles to a bridge. Johnson opened the trunk and held a flashlight while her husband pulled Engst onto the bridge.

“Crystal Herman claims that having seen enough,” she went to sit in the vehicle, but she heard Herman beat Engst to death with a shovel before dropping her in the Sheyenne River, the prosecutor said.

“Crystal heard two or three splashes,” the prosecutor said. “One splash was Amanda wrapped in a tarp and weighed down by cinder blocks that were tied to her by an extension cord and rope. The other was the shovel with the broken handle.”

'I just don’t understand'

It’s unclear what motivated Herman or why Johnson aided him. However, Johnson’s cooperation with law enforcement led to the discovery of Engst’s body in February 2016, according to her attorney, Nicole Bredahl.

Not realizing what happened, Engst’s family reported her missing in November 2015. The family said they last heard from Engst on Oct. 27, 2015. But it’s possible Herman and Johnson were using Engst’s phone to reply to her family, Peterson said.

The couple continued to use Engst’s vehicle, including when they robbed convenience stores in Buxton, N.D., and Perley, Minn., and committed a burglary in Grandin, N.D., in late October, law enforcement said. Herman is serving a prison sentence in Stillwater, Minn., in connection with the crimes, which at times involved a bat and bandanas that covered their faces, according to court documents.

At least two of Engst’s checks were made payable to Herman and Johnson, while others were believed to be forged, the transcript said.

Johnson was arrested Nov. 10, 2015, in Hillsboro, N.D., while driving Engst’s car, the transcript said. Herman was arrested separately, but evidence found inside the car linked him to the murder, law enforcement said.

Charges weren’t filed against Johnson until August 2017 and Herman until June 2018. The public defender’s office representing Herman declined a request for an interview.

Johnson is serving her sentence at the women's prison in New England, N.D. The Forum sent her an email through a system for contacting inmates but did not receive a response.

Johnson apologized to Engst’s family in May 2018 when she was sentenced, saying the killing weighed heavily on her. “I will have to live with that for the rest of my life, nothing like you guys would have to,” she said, according to the transcript.

Engst’s mother, Denise Stevenson, said during the hearing that her family’s lives have changed forever.

“And I just don’t understand why they had to take Amanda’s life, when she was the type of person that would give anything to anybody,” she said. “She was a very giving person and a caring person, and she did not deserve this.”