Utah children's book author Kouri Richins and her late husband, Eric Richins, were the "perfect" couple before Kouri was accused of poisoning Eric to death last year, according to her former coworker.

Linda King used to work with Kouri, 33, at a Home Depot in Summit County, where Eric, a 39-year-old contractor and masonry business owner, would stop in every day to pick up supplies.

"One day, one of his employees, he came in and said, 'Eric's out in the truck, but he really likes Kouri.' It was just like a silly thing," King told Fox News Digital in an interview.

By all appearances, they seemed like the perfect couple, King said. They were young and attractive and kind. Eric had the best laugh, and King would say funny things when he came by the store just to hear it.

UTAH MAN ALLEGEDLY POISONED BY AUTHOR WIFE BELIEVED SHE WAS HAVING AFFAIR: FAMILY SPOX

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)

"They were just perfect," King said. "Naturally in love."

However, in March 2022, King saw a post on Facebook about Eric's sudden death. The couple had been married nine years by that point.

UTAH CHILDREN'S BOOK AUTHOR, HUSBAND SPARRED OVER ‘CURSED’ MANSION BEFORE HIS ALLEGED MURDER

King heard that Eric had died of a brain aneurism. It was not until earlier this week, when news came out that Kouri had been arrested in Eric's death, that King learned he had died of fentanyl poisoning.

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)

"It just makes me sick to my stomach," King said, adding that she wants to give Kouri the benefit of the doubt, but the "evidence" against Kouri presented in an arrest warrant makes her feel "sick."

"I keep on saying to myself, ‘She’s not guilty until they find her really guilty,'" she tearfully added.

UTAH CHILDREN'S BOOK AUTHOR CHARGED WITH FATALLY POISONING HUSBAND

Prosecutors say Kouri poisoned Eric 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.

Kouri Richins, Eric Richins and their three sons

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

The couple also had been having financial disagreements prior to Eric's alleged murder, and his family spokesperson, Greg Skordas, told Fox News Digital on Thursday that Eric "had reason to believe" Kouri was having an affair during their marriage.

Eric also suggested to those who knew him that he feared for his life prior to the alleged poisoning and had taken his wife off of his will. The month prior to his death, on Valentine's Day in 2022, Eric suspected his wife was trying to poison him.

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

Eric Richins holding a deer with his son

Eric Richins took Kouri Richins off his will prior to his death; his estate is worth about $3.6 million. (Facebook/ Eric Richins)

On March 3, 2022, the night prosecutors allege that Kouri 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.

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

UTAH MAN FEARED FOR HIS LIFE PRIOR TO ALLEGED POISONING BY CHILDREN'S BOOK AUTHOR: WARRANT

Eric 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. Kouri is also facing charges of 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 growing his "successful" mansonry business. The obituary also describes him as a dedicated family man. (Facebook/ Kouri Richins)

Eric was not known to use drugs, and his family and friends knew him as a committed family man. An obituary for Eric describes him as an "avid outdoorsman and dedicated hunter." He enjoyed helping at his family's cattle ranch and growing his "successful" masonry business. 

Eric did absolutely everything in his power to provide his family with every possible opportunity to learn, grow, and have fun," his family wrote.

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

Kouri continues to argue in a 2022 lawsuit with her sister-in-law that she is entitled to her late husband's $3.6 million estate due to a prenuptial agreement.

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)

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

CLICK TO GET THE FOX NEWS APP

Richins' arrest 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."

Fox News' Ashley Pappa contributed to this report.