After confessing to killing his pregnant wife Shanann and their two children, Bella, 4, and Celeste, 3, in 2018, Colorado resident Chris Watts begun serving five consecutive life sentences at a Wisconsin prison without the possibility of parole. During his stay at the penitentiary, the convicted murderer struck up a correspondence with 65-year-old Cheryln Cadle, which is where he revealed the truth behind the horrific Aug. 13, 2018 murders.

According to Daily Mail, the Frederick, Colorado native outlined how he went about carrying out the murders. According to Watts' account, he attempted to smother Bella and Celeste before strangling his wife at the home they all shared.

Watts then revealed that the girls "woke up bruised and traumatized" after he had murdered their mother.  He then added that he drove them out to the site of the oil tanks and smothered them at the location. In recounting the details, he said that he was surprised that "little quiet Bella had a will to live." This revelation had not been previously been shared during interviews leading up to his confession.

READ: Why Do Men Like Chris Watts Become 'Family Annihilators'? A Look Inside

In the newly-released letters, he also admitted that he had been planning the crimes for quite some time, which countered his initial statement that the murders had been spontaneous.

"August 12th when I finished putting the girls to bed, I walked away and said, 'That's the last time I'm going to be tucking my babies in.' I knew what was going to happen the day before and I did nothing to stop it!" he revealed.

Even though he turned down countless interview requests and received hundreds of letters, it has been reported that he responded to the Illinois grandmother due to the fact that she believed he could "still make a difference in other people's lives and that his could be a 'story of redemption.'" After writing Watts on three occasions, she received a response. She then subsequently visited him three times, with each visit lasting around five hours. 

Ultimately, Watts gave Cadle permission to use his letters in her upcoming book, "Letters From Christopher: The Tragic Confessions of the Watts Family Murders," which will be released on Oct. 7. However, he stated she could only do so if she also included his "testimony of coming to God and the forgiveness he received" in the published work.

Following the admission of his guilt, those around the case have continued to deal with the aftermath. Shanann's father recently asked that people stop harassing his family online, while the law enforcement officials who worked on the case spoke out about the trauma that they have experienced after the conclusion of the investigation.

As for how Watts' life has been in prison, there have been conflicting reports. One insider shared that the convicted killer remains in "his own private hell" during his incarceration, while others have stated that he continues to receive multiple female visitors.

"Letters From Christopher: The Tragic Confessions of the Watts Family Murders" will be released on Oct. 7.

Chris Watts Chris Watts in court for his arraignment hearing at the Weld County Courthouse in Greeley, Colorado, on Aug. 21, 2018. Photo: Getty Images/RJ Sangosti