Shanann Watts' parents and brother have reacted with shock and disgust to Chris Watts' finally confessing to how he murdered her and their three children.

In an interview with Dr. Phil that will air on Monday, Sandra and Frank Rzucek were joined by their son to share their grief over the deaths of their daughter, her two children Bella and Cece, and her unborn son.

All were killed by Shanann's husband Chris Watts in Colorado in August last year after Shanann confronted her husband about an affair he was having.

He strangled Shanann in their home then drove to an oil field where he worked with her dead body and their two young daughters, who were still alive, in the car.

He then smothered three-year-old Celeste with a blanket, took her body out of the car then went back to do the same to four-year-old Bella who used her last breath to squeal: 'Daddy, no!'

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Shanann's father Frank, left, her mother Sandra, center, and her brother Frankie, right, were emotional throughout their interview

Murderer and victims: Chris Watts spoke about what happened on the night his wife and daughters were killed in a prion interview last month (above just months before the murders)

The harrowing details emerged this week for the first time since Watts was taken into custody.

'It's worse than we ever thought. We thought we'd heard the worst already, we had no idea it was worse than this,' Shanann's brother Frankie said.

Her mother cried at points in the interview and said the only thing keeping her alive was her faith.

'Those were my grandchildren. I loved them. They were mine. I cry all the time.

'There's many times that I just feel like giving up. If it wasn't for God I wouldn't be here,' she said.

Frank, Shanann's father, recounted the disturbing details of the murders to Dr. Phill who replied: 'I am so, so sorry.'

Watts gave investigators the sickening full account of the killings last month.

Shanann's father Frank's face was numbed by grief as he described how his son-in-law murdered his daughters and granddaughters

It began when Shanann, who had been on a business trip in Arizona, returned home in the early hours of August 13.

She and Chris had sex and he then brought up the fact that he'd been having an affair.

Shanann told him to end his relationship or risk never seeing his children again.

Her threat triggered him and he climbed on top of her.

With her husband straddling her, she pleaded for him to be gentle.

'Get off me … don’t hurt the baby,' she said, making reference to her unborn child.

Now andd then: A few hours later he spoke with Shanann before work and was confronted about his affair with Nichol Kessinger, which is when he strangled his wife (Watts in February on left during interview and on right in the only known photo of him taken the morning of the murders)

She was 15 weeks pregnant with a baby boy who they planned to call Nico.

'Every time I think about it, I’m just like, did I know I was going to do that before I got on top of her?' said Watts.

'Everything that happened that morning I just don’t - I don’t know… like, I try to go back in my head… I didn’t want to do this, but I did it... it just felt like there was already something in my mind that was implanted that I was gonna do it and when I woke up that morning, it was gonna happen and I had no control over it.'

He then read a Bible verse when Shanann had stopped breathing, saying: 'Forgive these people for they do not know what they do,”

Watts told authorities he threw away the sheets from the bed because Shanann evacuated her bowels when she died.

Watts also revealed he had not spoken to any family members since he was sentenced, which would explain why his father has insisted that his son is innocent.

After strangling Shanann, which he said took less than four minutes, Bella came into the room and was informed by her father that her mother was asleep.

'I was just getting the sheet off the bed and she walked in, and she had her little pink blanket with her,' said Watts.

Mistress: Shanann believed that Watts was having an affair long before that day, but it had been confirmed by a recent credit card charge (Watts and his mistress Nichol Kessinger above in July)

'She started crying a bit and was like, "What's wrong? What's wrong with mommy?"'

Watts then dragged Shanann down the stairs, at which point the couple's other daughter Celeste was woken up and began running around the house with her sister.

Shanann'ds body was then loaded into Watts' truck with her two daughters, who spent an hour in the vehicle with their dead mother's body.

'Daddy, it smells,' said Bella during the drive.

Once Watts arrived at his work site, he took Shanann's body out of the car and then returned to kill Celeste.

He smothered Celeste with a New York Yankees blanket while choking her neck and then tossed her body in an oil tank.

Bella sat silently and watched as her father killed her little sister.

When he returned from dumping Celeste, Bella asked quietly: 'Is the same thing gonna happen to me as Cece?'

Watts said he was not sure if he told her 'yes' or not at the time.

She put up a fight while he began to smother her in the same manner as her sister, making grunting noises and screaming out just before she died: 'Daddy, no!'

Celeste was able to fit into the opening in the oil tank but Bella had to be manipulated said Watts, who next went about burying his wife Shanann.

He raked away some weeds but then dumped the rake when it broke, before putting her and his unborn son Nico in a shallow grave.

Watts then went home, where he tossed the Yankees blanket and his clothes in a neighborhood dumpster.

He said there was no master plan and he is still not certain how he managed to act normal around people after these events transpired in early August.

Watts also said he did not even try to think up an alibi at any point.

'I had no time to really have a thought that was my own,' he explained that day.

One of the key reasons for Watts' rage and anger towards his wife was her decision to cut ties with his parents after an incident that occurred a few weeks before the murders.

Shanann declared that his parents could no longer see the girls after his mother served ice cream with peanuts at a party, despite his daughter's allergy to nuts.

'I don’t know if that had something to do with it... that something inside me just triggered it and then it just like, all that pent up from the wedding and everything,' said Watts.

'It’s like a long fuse that finally just went to its end.'

Watts said that he regretted the way he came to treat his family after he began dating Shanann, and revealed only his grandmother came to his wedding.

He said that he entered a guilty plea because he did not want to make his attorneys lie for the two to four years a trial would take to run its course.

'They would’ve done anything I told them to do... I don’t see how they can do that,' said Watts.

'Like, you know, that’s what attorneys do... you know, like, they take their defendant and they say hey, like, what happened, okay we’ll go with that story.'

When Watts was asked to go in for a polygraph test just days after Shanann and the girls were reported missing he said that he knew he was not walking out that day.

Jail was rough for him in Colorado he told the officials that day, saying that other inmates would scream out ways for him to take his own life.

In his final days before being transferred to his current prison, Watts actually believed that he was going to die.

He also found God.

'I never knew I could have a relationship with God like I do now...it’s like the amazing grace with all of this, but I just wish nobody had to pay any kind of price for this...I know there is a purpose for everybody, I just hope I can find mine.'