A Utah children's book author had a contentious relationship with her husband and was troubled by financial disagreements before she allegedly killed him with fentanyl, according to court documents.

Prosecutors say Kouri Richins, 33, poisoned her husband of nine years, Eric Richins, 39, with fentanyl on the evening of March 3, 2022, at their home in Kamas, just outside of Park City, while their three young sons were sleeping.

The couple reportedly had disagreements regarding a $3.75 million Wasatch County mansion prior to Eric Richins' death, according to search warrants obtained by KPCW.

Kouri apparently wanted to purchase the mansion, which she was hired to help sell, for $2 million, while Eric thought it was too expensive, KPCW reported.

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Kouri Richins, Eric Richins and their three sons

Eric Richins had five times the lethal dosage of fentanyl in his blood. Fentanyl is an opioid about 50 to 100 times more potent than morphine. (Facebook/ Kouri RIchins)

The warrants show Kouri closed a deal on the 22,000-square-foot home March 5, 2022, about day after Eric's death. His family told authorities they thought Eric had plans to tell her not to purchase the mansion, KPCW reported.

Two weeks after Eric's death, Kouri reportedly relisted the home for $5 million, and it is under contract for $3.75 million.

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The home, initially valued at $7.6 million, has been under construction since 2017, according to TownLift

Kouri Richins' sold mansion

Warrants show that Kouri closed a deal on the 22,000-square-foot home on March 5, 2022, about a day after Eric's death, despite the fact that Eric had plans to tell her not to purchase the mansion, KPCW reported. (TownLift, Will Scadden)

Construction initially paused in 2019 after an "unattended death." The owner of the home moved out of the country afterward and sold it to a newlywed couple in January 2022.

The newlyweds planned to finish construction on the house when the husband unexpectedly died shortly after their purchase. Kouri Richins' real estate company, K Richins Realty, then purchased and sold the home.

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"That place is cursed," one person said of the house on TownLift's Instagram page.

On March 3, 2022, the night prosecutors allege Kouri Richins killed her husband, she allegedly served her husband a cocktail to celebrate the home sale.

Kouri Richins headshot

This photo provided by KPCW.org shows Kouri Richins at the KPCW studio in Park City, Utah, April 12, 2023.  (KPCW.org via AP)

She later told authorities she left him briefly to check on one of her three sleeping children, and when she returned, she found Eric unresponsive, according to a warrant. 

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Eric had five times the lethal dosage of illict fentanyl in his blood, according to the medical examiner.

Kouri Richins is also charged with possession of GHB, commonly known as the "date rape drug."

Kouri and Eric Richins smile together

An obituary for Eric Richins describes him as an "avid outdoorsman and dedicated hunter." He enjoyed helping his family's cattle ranch and expanding his mansonry business. The obituary also describes him as a dedicated family man. (Facebook/Kouri Richins)

Her charges are based on officers' interactions with Richins and an unnamed acquaintance who apparently told Summit County authorities that she sold fentanyl to the mother of three, who had asked for "some of the Michael Jackson stuff," the warrant states.

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Kouri is also in a legal battle with Eric's sister, Katie Richins-Benson, over the ownership of her home. Kouri purchased the Kamas home with Eric from Richins-Benson nine years ago. Eric took Kouri off his will prior to his death; his estate is worth about $3.6 million. 

Kouri and Eric Richins smile together

Utah prosecutors are accusing Kouri Richins, 33, of poisoning her husband Eric Richins, 39, with fentanyl last year at their home in Kamas, outside Park City, while their three young sons were sleeping. (Facebook/Kouri Richins)

Last year, Kouri sued Richins-Benson for $3.6 million, alleging she is still a trustee due to her prenuptial agreement. Richins-Benson, in turn, argues that Kouri is not entitled to her brother's estate, according to civil court documents obtained by Fox News Digital.

The day after Eric's death, his sisters apparently went to the couple's Kamas home and "began threatening and verbally accosting Kouri," a 2022 complaint states.

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"After Kouri insisted that the sister leave, the sister asserted that Kouri did not own the Family Home and that she would ensure Kouri was kicked out of the Family Home," her attorneys alleged in the document.

Eric and Kouri Richins at a football game

Charges filed against Kouri Richins are based on officers' interactions with Richins and an unnamed acquaintance who apparently told authorities she sold fentanyl to the mother of three.  (Facebook/Kouri Richins)

Kouri was also sued by two of her tenants for what they described as unlivable conditions due to mold and mold spores in a home they purchased from Kouri in 2020, according to the lawsuit.

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Her arrest also comes two months after she appeared on TV to promote her children's book about grief, "Are You With Me?"

A description for the book, which sells for $14.99 on Amazon, states that "Are You With Me?" is "a must-read for any child who has experienced the pain of loss, and for parents who want to provide their children with the emotional support they need to heal and grow."

Editor's note: This article has been updated to reflect that K. Richins Realty LLC was not the listing agent of the Wasatch County mansion but the next buyer.