What went wrong in the mind of a young husband and father that drove him to brutally murder his pregnant wife and daughters?
It's a question to which we may never know the answer, and one that will haunt their friends and relatives forever.
This was a sickening crime that seemed all the more incomprehensible because of the happy photos that littered the Colorado family's social media accounts. It is a crime for this era, another chilling warning of what our endless streams of perfect Instagram pictures can conceal, reports news.com.au.
The world stared into Chris Watts' eyes in those photos, wondering if there was a certain dead, hollowness to them.
In photos taken less than two weeks before he strangled wife Shanann and their girls, the kids played happily with their mother during a family holiday at Myrtle Beach, South Carolina.
Watts stood to the side, apparently deeply uninterested in his wife — who was 15 weeks pregnant — or his daughters Bella, 4, or Celeste, 3. We can only wonder what the 33-year-old was thinking.
THE 'PERFECT' FAMILY
It is now clear life for the family in the small town of Frederick, population 8000, was not as rosy as it looked on social media. Court records showed the couple had money problems, filing for bankruptcy in June 2015, six months after Watts was hired as an operator for oil and gas giant Anadarko Petroleum.
Shanann was working in a children's hospital call centre. They reported total earnings of $120,000 in 2014 but $96,000 in unsecured claims — including thousands of dollars in credit card debt, student loans and medical bills — along with a mortgage of about $4000 a month.
But Shanann, 34, seemed to believe love would see her beautiful family through anything.
In April this year, during a work trip to New Orleans, she wrote of her husband on Facebook: "He's my rock! He takes care of us girls unconditionally! Thank you baby for holding down the fort this weekend! Love you."
In a video shared online, she described how she met Watts after he sent her a friend request on Facebook, and how lucky she was that he had stuck by her through her battle with autoimmune disease lupus.
"One thing led to another and eight years later we have two kids, we live in Colorado and he's the best thing that has ever happened to me," she said. "I let him in … he knew me at my worst and he accepted me. Through sickness and everything he's been there. When I met Chris I pushed him away, I gave every excuse for him to run, I gave him an out every single day … But he stuck around because he was the one for me, I can't tell you how wonderful he is."
She shared a video of Bella singing to her "hero daddy", and in May, filmed her husband as she revealed she was pregnant for the third time. "That's awesome," says a smiling Watts. "I guess when you want to, it happens ... Wow."
On June 19, Shanann sent Watts an ultrasound picture of their unborn third baby. "Little Peanut! Love her/him already!!!" Watts replied.
Shanann was so delighted with his response, she shared the exchange on her Facebook page writing: "I love Chris! He's the best dad us girls could ask for."
He was to kill Shanann before the son they decided to call Niko could take his first breath.
Around this time — two months before the grisly killings — Watts was embarking on an affair with colleague Nichol Kessinger, who worked in Anadarko Petroleum's environmental department.
He was not wearing a wedding ring when they were introduced and when they met outside of work in June, he told her he was in the final stages of a divorce, she said later. He wanted a baby boy, but was concerned about finances, Nichol told investigators.
Shanann wasn't stupid. She noticed her husband's "suspicious behaviour" and credit card notifications for restaurant bills while she was away for work, prosecutor Michael Rourke said after the sentencing this week.
She confronted him repeatedly over whether he was having an affair, but Watts had no answers for his pregnant wife, who was desperate to salvage their relationship and keep the family together. The prosecution said he was longing to make "a fresh start" with Nichol.
Shanann spent much of the summer working and staying with her parents and daughters in North Carolina, while an infatuated Watts wined and dined his new girlfriend, researching jewellery and holiday destinations online.
In July, Shanann texted him: "I realized during this trip what's missing in our relationship! lt's only one way emotions and feelings. I can't come back like this. I need you to meet me halfway." Watts replied that he was sorry and he loved her.
She answered: "I try to give you space, but while you are working and living the bachelor life I'm carrying our 3rd and fighting with our two kids daily and trying to work and make money. It's not hard texting love you and miss you. If you don't mean it then I get it, but we need to talk."
In the weeks before Watts killed her, she kept trying to save their marriage, giving him books on self-help and relationship counselling. He threw them away.
On the night of August 5, she texted him: "I missed holding you and snuggling with you. I missed eating with you, watching tv with you. I missed staring at you, I missed making love with you. I missed everything about you.
"I couldn't wait to celebrate 8 years with you … If you are done, don't love me, don't want to work this out, not happy anymore and only staying because of kids, I NEED you to tell me."
Later, she texted again: "I just don't get it. You don't fall out of love in 5 weeks."
A week later, Watts did the unfathomable.
'HE'S GOING OUT TO POUR OIL ON THE BODIES'
On Monday, August 13, Shanann returned from a work trip to Arizona shortly before 2am. Watts later told police they had an "emotional conversation", in which he said he wanted to end the relationship, and she had walked out — but police found she had not taken any of her things.
When the 34-year-old missed a doctor's appointment the next morning and did not answer her phone, her friend Nicole Utoft became worried.
Nicole called around at midday. When no one answered the door, she contacted Watts and reported Shanann and her girls missing to the police.
At around 1.40pm, a Frederick police officer was dispatched to the family home. The trio was officially missing.
The next morning, an oddly restrained Watts spoke to the media on his doorstep, telling the cameras of his anguish.
He said that when his wife had failed to return his calls and text messages on Tuesday, as well as those from her friends, he had become concerned.
When Nicole called to say she had found the house empty, he recounted how he had rushed home and found an empty house. Of course, he already knew he would.
"Last night, I had every light in the house on," the dry-eyed, preternaturally calm father told Colorado TV station KMGH. "I was hoping that I would just get ran over by the kids running in the door, just barrel-rushing me, but it didn't happen."
Looking directly into the lens of a Denver 7 camera, he said: "I have no idea, like, where they went. I don't even feel like this is real right now. It's like a nightmare I can't wake up from."
He told KUSA-TV his family's disappearance was "earth-shattering", adding: "If somebody has her just please bring her back. I need to see everybody, I need to see everybody again; this house is not complete without anybody here."
Nichol, 30, said she was mystified when she saw on the news that the man she was dating was very much still married, and his wife was 15 weeks pregnant. She called and texted him repeatedly, but he changed his story about the divorce, showed little emotion about his family's disappearance, and tried to change the subject.
"It got to a point that he was telling me so many lies that I eventually told him that I did not want to speak to him again until his family was found," she told the Denver Post.
One person immediately suspected he was guilty. Shanann's mother, Sandra Rzucek.
"She stated that Christopher is acting 'weird' and out of the ordinary," read a police report obtained by the Post after the sentencing. "She said that Christopher is telling people, 'He has to go to work,' and that just doesn't seem right. She felt that he is going out to pour oil on the bodies to dispose of them somewhere."
'THE QUESTIONS THAT WILL HAUNT THEM'
The pretence could not continue for long.
On Wednesday, August 15, two days after the family's disappearance, Watts was arrested on suspicion of triple murder and first-degree unlawful termination of a pregnancy.
The following day, he led police to where he had dumped three bodies on the property of Anadarko Petroleum. Shanann's body was buried in a shallow grave, while Bella and Celeste were submerged in drums containing crude oil.
Nichol called the police to report the stories Watts had told her.
But the 33-year-old dad wasn't finished lying. In an affidavit unsealed on August 20, his egregious defence was revealed. Watts claimed his wife had strangled the girls, and he had then strangled her to death in retaliation.
During the killer's arraignment the next day, Shanann's father Frank Rzucek wept in court. Her brother Frankie posted on Facebook: "My blood is boiling. I just want 30 seconds alone with that heartless psychopath."
On Tuesday, November 6, Watts pleaded guilty on nine counts — including murder, the unlawful termination of a pregnancy and tampering with a dead body — in exchange for an agreement prosecutors would not pursue the death penalty.
This Monday, Watts was handed three consecutive life sentences for his heinous crimes. As he was sentenced, the world finally saw him express emotion, as tears rolled down the murderer's cheeks.
His spouse's father called him an "evil monster", telling the court "life will never be the same" without Bella, Celeste, Shanann and her unborn baby Niko.
"I trusted you to take care of them, not kill them. And they also trusted you," said Frank.
"You may have taken their bodies from me but you will never take the love they had from me.
"They loved us more than you will ever know, because you don't know what love is."
It was a portrait of a mother who wanted the dream family life, and her sweet, innocent children, all victims of a "heartless" murderer.
Watts spoke just once at the sentencing hearing, to decline the opportunity to give a statement and explain why he did it.
"How could a seemingly normal husband and father annihilate his entire family? For what?" District Attorney Mr Rourke asked the court.
"Those are the questions that will always haunt anyone who was involved in the investigation. I don't think there is ever going to be a satisfactory answer for anyone."
Shanann was a "a woman of love", the priest at her funeral told mourners. She loved her family and friends, existing in a totally different world to her twisted husband.
"She was a woman of determination," said Father John Forbes. "She had dreams to be fulfilled, and she worked towards to those dreams. She wanted to make a difference.
"She wanted to be an exceptional wife and mother."