A Utah man feared for his life before his wife, a children's book author, allegedly killed him with fentanyl, according to Summit County 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 month prior, on Valentine's Day in 2022, Eric Richins suspected his wife was trying to poison him, a warrant for her arrest states.

"Eric and the Defendant had a Valentine's Day dinner at their Kamas home. Shortly after the dinner, Eric became very ill. Eric believed that he had been poisoned. Eric told a friend that he thought his wife was trying to poison him," the warrant reads.

UTAH CHILDREN'S BOOK AUTHOR CHARGED WITH FATALLY POISONING HUSBAND

Kouri Richins, Eric Richins and their three sons

Eric Richins had five times the lethal dosage of fentanyl in his blood. (Facebook/Kouri RIchins)

On March 3, 2022, the night prosecutors allege Kouri Richins killed her husband, she allegedly served her husband a cocktail to celebrate a home sale. Kouri owns a real estate firm called K Richins Realty LLC.

LORI VALLOW TRIAL: HEAR ‘CULT MOM’ AND HER SISTER SPEAK AFTER VALLOW'S CHILDREN FOUND DEAD

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

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)

Eric Richins had five times the lethal dosage of illict fentanyl – an opioid that is 50 to 100 times more potent than morphine – in his blood, according to the medical examiner..

UTAH STUDENT AT ‘WORLD CLASS’ BOARDING SCHOOL DIED OF SEPSIS AFTER COMPLAINTS WERE IGNORED: LAWYER

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

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 of Park City while their three young sons were sleeping. (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.

UTAH HIKER, 70, FIGHTS OFF MOUNTAIN LION WITH A ROCK AFTER HE'S AMBUSEHD IN CANYON

Authorities said they determined during their investigation that despite Richins' statements saying she left her phone in her bedroom when she went to check on her children the night of March 3, 2022, her phone activity indicated that it had been locked and unlocked multiple times during that period and showed no physical movement.

Additionally, messages were sent and received during that period but deleted, investigators said.

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 that she sold fentanyl to the mother of three. (Facebook/Kouri Richins)

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

CLICK TO GET THE FOX NEWS APP

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."