The mistress of killer dad Chris Watts has revealed she "felt so sad" when she learned her boyfriend was a cheat and a killer.
Nichol Kessinger was having an affair with the dad-of-two before he strangled his pregnant wife Shannan and smothered their two children, aged four and three, at their home in Frederick, Colorado, US.
The murderer dumped the children's bodies in an oil tank before killing his wife and dumping her body in a shallow grave in August, 2018.
The sick husband was playing the victim and told police he had no idea where his family was.
Watts later told cops he brutally murdered his family just to be with his mistress Nichol Kessinger, who was left stunned at the news.
She told the Denver Post: "I don’t think there is a logical explanation for what he did. It’s a senseless act, and it’s horrific.”
Nichol had approached police before Watts' arrest and attended several interviews to help them with their enquiries.
She was working as a geologist when she met the killer in the environmental department of a contractor.
He would wait in the office before being sent to his next job but the pair never spoke.
But in the middle of June, Watts eventually introduced himself to Nichol and, after noticing he wasn't wearing a wedding ring, the pair chatted and hit it off.
Nichol revealed: “We had just met. I barely knew him. When he spoke to me, he was very soft spoken. He appeared to be a good listener."
She was told by Watts he was a dad to two young children who was in the process of getting divorced from his wife.
Nichol admitted: “I believed him.”
When the pair met again outside of work in June she asked him if the divorce had been finalised.
Watts revealed it was close but not yet done as they had to iron out some financial details.
However, in July they began a physical relationship and met up with each other four to five times a week.
Nichol said: “He made me believe that he was doing all of the things that a rational man and good father would do."
But on August 13, the day his girls and wife disappeared, he texted Nichol to say he had been busy and continued their work day like normal.
However, around 3.45pm, Watts texted his mistress to inform his family had "gone".
He told her his wife had taken their kids to a playdate but never returned.
Watts, however, seemed remarkably calm but Nichol soon became concerned when media turned up outside his house.
His lies started to unravel when she soon learned of his pregnant wife.
She admitted: “I was very confused why the media was at his house.
"When I read the news, I found out he was still married and his wife was 15 weeks pregnant."
Nichol was stunned when she found out Watts had lied to her this whole time: “I thought, ‘If he was able to lie to me and hide something that big, what else was he lying about", she said.
On August 15, Watts was arrested for the murder of his wife and two daughters, which she saw on the news.
Nichol admitted: “I just felt so, so sad."
Watts is serving five life sentences plus 48 years in prison without the possibility of parole at the Dodge Correctional Institution in Wisconsin.
Ever since his arrest, Nichol was convinced he was a murderer after the web of lies.
“He’s a liar. He lied about everything", she said.
