“She knew she did wrong, so she just probably accepted it,” Matheny tells PEOPLE exclusively of Brooke Crews, in his first comments about Crews’ guilty plea earlier this week in the death of Savanna LaFontaine-Greywind, 22.
“I think she [Crews] didn’t want a trial because they had way too much against her,” Matheny says.
According to authorities, Crews, 38, killed LaFontaine-Greywind in August after the younger woman visited her apartment in the complex in Fargo, North Dakota, where they both lived.
LaFontaine-Greywind was eight months pregnant when she died. Police have not said how, when or where she was killed or under what circumstances her baby was born, but they did say she was killed by “homicidal violence.”
The Fargo police chief called her slaying “a cruel and vicious act of depravity.”
She vanished on Aug. 19 after leaving her family’s basement apartment to visit Crews on the third floor. The older woman had asked her to model a dress she was sewing.
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LaFontaine-Greywind’s plastic-wrapped body was found more than a week later, on Aug. 27, in the nearby Red River. Crews and her boyfriend, 32-year-old William Hoehn, had already been taken into custody at that point after police said they found Crews with LaFontaine-Greywind’s baby daughter in her apartment.
DNA testing ultimately confirmed this suspicion and the child, named Haisley Jo, was returned to Matheny’s custody.
On Monday morning, Crews pleaded guilty to charges of conspiracy to commit kidnapping and conspiracy to commit murder as well as giving false information to police. (Hoehn is set to go on trial on those same charges, to which he has pleaded not guilty.)
“I guess it makes things easier for her, because now she doesn’t have to go to trial,” Matheny tells PEOPLE.
“I wasn’t surprised that she changed it [her plea],” he says. “She should have pleaded guilty right away.”
Until she was killed, LaFontaine-Greywind and Matheny were planning on moving in together in September, her family has said. They had reportedly been dating for seven years. Their baby was due Sept. 20.
Crews faces up to life in prison without the possibility of parole. Her sentencing is scheduled for Jan. 16.
Crews’ attorney told PEOPLE she decided to plead guilty after reviewing the evidence against her during discovery. “She made the decision to take responsibility,” he said.
Prosecutors provided a brief summary of the case at Monday’s hearing and said Crews had planned to “register” LaFontaine-Greywind’s daughter and “raise the child as her own.”
LaFontaine-Greywind was killed by violence allegedly inflicted by Crews and Hoehn, prosecutors said.
They allegedly conspired “to murder Savanna Marie LaFontaine-Greywind in order to obtain her fetal child,” according to charging documents obtained by the Minneapolis Star Tribune.
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Court documents previously obtained by PEOPLE show Crews and Hoehn gave conflicting accounts of how they came to have the baby girl:
Hoehn allegedly told police he arrived home from work on Aug. 19 to find Crews cleaning up blood in the bathroom. She was also holding an infant and allegedly told him, “This is our baby, this is our family.”
Hoehn allegedly told police he removed garbage bags containing bloody towels and his own bloody shoes and left them in a dumpster.
But Crews allegedly told detectives that she had invited LaFontaine-Greywind to their apartment on Aug. 19 and, bizarrely, taught the pregnant woman how to self-induce birth by breaking her own water. Crews claimed the other woman then left — only to return two days later to give her her newborn.
Speaking to PEOPLE following the confirmation of her daughter’s death, Norberta Greywind said she was thankful to know her granddaughter is safe.
“She’s all we have now,” Greywind said. “Knowing we have her, it gives me peace.”