A Utah woman who published a children's book on processing grief following the death of her husband last year has now been charged with his murder, court documents show.

Kouri Richins, 33, faces charges including aggravated murder in connection with the death of her husband, Eric Richins, 39, who was found dead at the foot of their bed on March 4, 2022, according to the probable cause statement.

While appearing on a "Good Things Utah" segment last month on Salt Lake City ABC affiliate KTVX to promote her new children's book, Kouri Richins said her husband died "unexpectedly." Prosecutors allege that Eric Richins was poisoned by a lethal dose of fentanyl on the night of March 3, 2022, according to the charging document.

Kouri Richins allegedly told police following his death that they were celebrating her closing on a house for her business that night and she "made Eric a Moscow Mule in the kitchen and brought it to their bedroom where Eric consumed it while sitting in bed," according to the probable cause statement.

She allegedly said she went to sleep with one of their children who was having a night terror and returned to her and her husband's bedroom around 3 a.m., where she found him "cold to the touch," according to the document.

An autopsy determined that Eric Richins died from a fentanyl overdose, and that the level of fentanyl in his system was five times the lethal dosage, according to the document. The medical examiner indicated the fentanyl was "illicit fentanyl," not medical grade, and that it was likely ingested orally, according to the document.

Detectives obtained a search warrant for their residence following the toxicology report, including for electronics, according to the document.

Kouri Richins allegedly told law enforcement that upon going to bed she did not use her phone until calling 911, though the phone had been locked and unlocked multiple times during that period and messages had been sent and received during that time and deleted, according to the document.

A search of Kouri Richins' phone also uncovered "several communications" with an acquaintance of hers who had various drug counts, according to the document.

During an interview with detectives earlier this month, the acquaintance allegedly said that sometime between December 2021 and February 2022, Kouri Richins allegedly texted them asking for "prescription pain medication for an investor who had a back injury," and the acquaintance left hydrocodone pills at a house the defendant owned and was flipping, according to the document.

About two weeks later, Kouri Richins allegedly contacted the acquaintance again because "her investor wanted something stronger and asked for 'some of the Michael Jackson stuff,'" and "asked specifically for fentanyl," the document stated. The acquaintance allegedly procured 15 to 30 fentanyl pills in exchange for $900 on Feb. 11, 2022, according to the document.

Three days later, following a Valentine's Day dinner at their home, Eric Richins became "very ill" and "believed that he had been poisoned," the document stated.

"Eric told a friend that he thought his wife was trying to poison him," the probable cause document stated.

Kouri Richins allegedly contacted the acquaintance about two weeks later "asking for another $900 of fentanyl pills," which were procured on Feb. 26, 2022, the document stated.

"Six days later, on March 4, 2022, Eric was found dead of a fentanyl overdose," the document stated.

Kouri Richins has also been charged with three counts of possession of drugs with intent to distribute.

ABC News has reached out to her attorney for comment. Her next hearing is scheduled for May 19, according to KTVX.

Kouri and Eric Richins were married for nine years and had three young sons together, according to his obituary.

She told KTVX during her interview last month for "Good Things Utah" that his death "completely took us all by shock."

"My kids and I kind of wrote this book on the different emotions and grieving processes that we've experienced last year," she said. "[I am] hoping it can kind of help other kids deal with this and kind of find happiness some way or another."

The dedication of her book, which was published in March, states it is to "my amazing husband and a wonderful father."