'He Lied About Everything': Unwitting Mistress Of Confessed Family Murderer Chris Watts Speaks Out

The girlfriend of a Colorado man who pleaded guilty to killing his pregnant wife and children says he lied to her about his marriage status.

Earlier this month, Christopher Watts admitted killing wife Shanann Watts, 34, and daughters Bella, 4, and Celeste, 3.

Watts told police he'd been having an affair with a coworker and revealed to his wife that he wanted to "go through with a separation," according to an arrest affidavit obtained by Oxygen.com back in August. 

Now that coworker, Nichol Kessinger, has spoken to the Denver Post about their relationship.

She told the newspaper that when she met Watts at Anadarko Petroleum, where they both worked, she noticed he wasn’t wearing a wedding ring.

“When he spoke to me, he was very soft-spoken. He appeared to be a good listener,” Kessinger told the paper.

She said at some point during their affair, which she described as brief, Watts claimed to be separating from his wife and near the end of divorce proceedings, Kessinger said.

“I believed him,” she said.

Kessinger told the Denver Post that she and Watts started having intimate relations in July, and saw each other about five times a week. That same month, Kessinger said he asked her to help him find an apartment for him and his daughters.

“He made me believe that he was doing all of the things that a rational man and good father would do,” she said.

Kessinger said she didn’t know that her lover was still married until his family was reported missing on the news.

“When I read the news, I found out he was still married and his wife was 15 weeks pregnant,” Kessinger said. “I thought, ‘If he was able to lie to me and hide something that big, what else was he lying about?’ ”

She said that when she approached him about his lies, he tried to change the topic.

“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 said.

Kessinger told the Denver Post that she believes that her former over killed his family.

“He’s a liar,” she said. “He lied about everything.”

Before Watts admitted to killing his family, he changed his story several times including at one point maintaining that he only killed his wife, and that he did so in a fit of rage after she murdered their daughters, supposedly upset at the fact that he was having an affair and wanted a separation.

The high-profile case is being reexamined in the season premiere of "Criminal Confessions," airing Saturday, Dec. 7 at 6pm ET/PT on Oxygen.