Chris Watts had a loving wife, two daughters and a baby on the way. Then he met Nichol at work.

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The word 'monster' is often overused, and yet it aptly sums up who Chris Watts is.

He is currently serving three consecutive life sentences for the murder of his 34-year-old pregnant wife Shanann, and their daughters Bella, four, and Celeste, three, in Colorado in August 2018.

Watts murdered his family in cold blood. Yet he blames one person for his decision — the woman who he was having an affair with at the time.

And in his prison letters about her, he refers to her only as "Jezebel".

In the Christian religion, a Jezebel is considered an immoral woman who deceives people to get what she wants. In Watts' mind, his former mistress Nichol Kessinger is to blame for his callous actions.

The courts didn't agree, handing Watts a sentence without the possibility of parole.

Here's exactly what happened in the tragic Watts family murders.

Watch the trailer for American Murder, the Netflix documentary that follows this case. Post continues below.

What happened to Shannan Watts?

Watts and Shannan first connected on Facebook in 2010, when he came up as a suggested friend.

"I was in a really, really, really bad place, and I got a friend request from Chris on Facebook," Shanann said in a May 2018 Facebook Live video.

"I was like, 'Oh, what the heck, I'm never going to meet him.' Accept."

She said "one thing led to another" and they eventually married and moved to Colorado together in 2012, per The Denver Post.

There, the couple had two children: Bella, born in December 2013, and Celeste, born in July 2015.

From the outside, the Wattses were a happy family. But there was a sinister underbelly.

A family friend told People in August 2018 the couple had been having "marital problems" and had previously struggled with their finances.

Meanwhile, a contractor who worked for Watts said he watched the father-of-two change over the summer of 2018.

"I watched him get more and more unhappy with his life," he told People.

"He went from being a friendly guy to being withdrawn and angry. I saw him lose his temper over little workplace annoyances. He had an irritable side with the contractors. He could be combative."

Shanann with her daughters. Image: Facebook.

On August 13, Shanann's close friend Nickole Atkinson reported her, Celeste and Bella missing.

Atkinson had dropped Shanann home from a work trip about 2am, but when she hadn't heard from her friend a few hours later, she called Watts to ask where she was.

It was then, she said, that Watts made a surprising disclosure.

"I didn't find out that they were going to separate or anything like that until I called Chris that morning," she told ABC in 2018.

"When I called him and asked him where she was, that's when he told me and I basically told him that that wasn't my [concern] at that particular moment, because it wasn't and that their business was their business."

At about 1:40pm, Atkinson reported her friend missing.

Watts originally fronted news cameras with a desperate appeal for help to find his wife and two young daughters.

However, the truth emerged when their bodies were recovered from an oil field owned by the petroleum company that Watts worked for, on August 17.

Shanann was 15 weeks pregnant, Atkinson said.

Watts' wife and his unborn son were buried in a shallow grave, and his daughters submerged in crude oil vats.

Initially he told police that his wife had left him and taken the children. He later tried to claim that she had killed the girls, but eventually confessed to the crimes and pleaded guilty.

A more accurate version of what happened that night was then revealed.

In his confession, Watts said Shanann returned from the work trip at 2am and they got into an argument, during which he admitted to having an affair.

He claimed when Shanann threatened to leave and deny him custody of the children, he "snapped" and strangled her. He then transported her body to an oil field that belonged to his employer and buried her, while his two girls waited in the car.

He then smothered his daughters with a blanket and disposed of their bodies in vats of crude oil.

The affair.

Nichol Kessinger was a crucial witness in the case.

Kessinger and Watts both worked at the oil company where Watts hid the bodies.

Kessinger said he introduced himself to her at work in June 2018. She thought Watts was divorced, as he didn't wear a wedding ring and he had claimed that he was separated from his wife.

She said she believed him and they began a sexual relationship in July, seeing each other four or five times a week.

"He made me believe that he was doing all of the things that a rational man and good father would do. He's a liar. He lied about everything," she said to the Denver Post.

Chris Watts and Nichol Kessinger during their affair. Image: Facebook.

Kessinger was not and is not suspected of any wrongdoing or involvement in the murder.

"I kept asking him, 'What did you do, Chris? What did you do?'" she said to police at the time. "I asked, 'Where's your family?'"

"I texted Chris one last time, and I told him, 'If you did anything bad, you're going to ruin your life and you're going to ruin my life. I promise you that'. And he responded, 'I didn't hurt my family, Nicky.' And that was the last text. I never said another word to him after that."

In November 2018, Watts pleaded guilty to nine charges in exchange for being spared a possible death sentence, The New York Times reports.

Watts will spend the rest of his life in a small cell at a notorious maximum-security prison in Wisconsin.

In the years since being convicted, several handwritten notes from Watts have been obtained and published by various media outlets.

In one published by the New York Post, Watts admitted he had been plotting the murders for some time, so that he could be with Kessinger. It's in this letter that Watts describes Kessinger as a "Jezebel".

"I was having an affair with this girl and I ended up in love with two women at the same time. It's what led up to what happened. She is of evil spirits, like Jezebel."

A similar note from 2020 read: "The words of a harlot have brought me low. Her flattering speech was like drops of honey that pierced my heart and soul. Little did I know that all her guests were in the chamber of death. How did I let this happen? The blessings you have bestowed upon me were right in front of me, and still I followed the perfume of a strange woman."

He added: "Jezebel was the forbidden fruit, and it was costly."

Shanann Watts and her daughters Bella and Celeste. Image: Facebook.

It's been reported that Watts has become heavily religious amid his time incarcerated.

Watts said he never read the Bible before entering prison, but has now read it cover to cover.

"I never knew I could have a relationship with God like I do now... it's like the amazing grace with all of this," he said, according to a transcript from the Colorado Bureau of Investigation.

For Shanann, Bella and Celeste's family, they have to live with the grief of losing their loved ones.

"We would die for our family to be back right now. (I have) a lot of memories. When I walk through that front door I look up at the balcony, and that is where my grand girls would be every day when I came home from work. To this day I look at that balcony. It is very hard," Shanann's father told CBS News through tears.

"Now, we have to look back on memories every day of the good times. And we had good times."

If this has raised any issues for you, or if you just feel like you need to speak to someone, please call 1800 RESPECT (1800 737 732) – the national sexual assault, domestic and family violence counselling service.

Mamamia is a charity partner of RizeUp Australia, a national organisation that helps women, children and families move on after the devastation of domestic and family violence. Their mission is to deliver life-changing and practical support to these families when they need it most. If you would like to support their mission you can donate here.

Feature Image: Netflix.