The horrific story was relived in the Netflix documentary, American Murder: The Family Next Door:
In 2018, Chris Watts strangled his 15-week pregnant wife Shanann before also killing the couple's daughters – four-year-old Bella and three-year-old Celeste – in Colorado.
He was sentenced to life imprisonment later that same year in November after admitting he was guilty as part of a plea deal to escape the death penalty.
The chilling texts he sent Nichol Kessinger just before murdering his family and dumping their bodies at the oil field he worked at have since been exposed.
The final text conversation between Kessinger and Watts was first revealed when Watts was being interviewed by police.
The first message sent by Kessinger states: "If you did something bad, you’re going to ruin your life. And if you did something bad, you’re going to ruin my life. I promise you that."
Watts responded by telling his mistress he 'didn't hurt' his family. However, after being arrested, he added: "Just don’t forget the person that you knew me to be when you were with me."
Watts was reportedly planning to divorce Shanann, however the mother-of-two is said to have been fighting to save the pair's marriage.
Kessinger and Watts had been seeing each other for two months before he murdered his family.
While not ruling out their relationship may have formed part of the motivation for the attacks, Kessinger said she thought Watts could have also been driven by money.
However, she also added she 'legitimately [thought] his cheese was sliding off his cracker long before he met [her]'.
The official synopsis reads: "In 2018, 34-year-old Shanann Watts and her two young daughters went missing in Frederick, Colorado. As heartbreaking details emerged, their story made headlines worldwide.
"Told entirely through archival footage that includes social media posts, law enforcement recordings, text messages and never-before-seen home videos, director Jenny Popplewell pieces together an immersive and truthful examination of a police investigation and a disintegrating marriage.
"American Murder: The Family Next Door is the first film to give a voice to the victims."
Many have praised the family's neighbour after the documentary revealed he alerted police when he noticed Watts acting strangely.
However, other viewers have been left in floods of tears over the harrowing footage and accounts.
American Murder: The Family Next Door is currently available to watch on Netflix. It was first released on 30 September, 2020.
If you have experienced a bereavement and would like to speak with someone in confidence contact Cruse Bereavement Care via their national helpline on 0808 808 1677Featured Image Credit: Netflix