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Chris Watts Was Allegedly Cheating on Wife Shanann with Coworker Before Murdering His Family: Authorities

Steve Helling

Colorado triple murder suspect Chris Watts was “actively involved in an affair with a coworker” before killing his family last week, according to allegations in court documents obtained by PEOPLE.

Watts, who has been charged with the first-degree murders of his 15-weeks-pregnant wife, Shanann, and their two children — 4-year-old Bella and 3-year-old Celeste — had allegedly denied the affair to police, an arrest affidavit shows. Authorities said they carried out a two-day investigation and confirmed the infidelity, however.

Investigators have redacted several lines of the affidavit in the paragraph pertaining to the alleged affair. The coworker has not yet been identified.

Chris’ marital impropriety was one of many blockbusters in the affidavit, which was released on Monday. He also allegedly admitted he killed Shanann — but only after, he claimed, he “went into a rage” when she strangled one of their daughters.

In addition to murder, prosecutors have charged Chris, 33, with three counts of tampering with a dead body and unlawful termination of a pregnancy in the first-degree. He was taken into custody on Wednesday night, two days after Shanann, was reported missing by a friend about 12 hours after they got back from a business trip.

Her body and the bodies of her girls were found on Thursday.

In the intervening days, as investigators worked on what appeared to be a missing persons case, Chris initially said that he had talked to Shanann on Monday after waking up about 5 a.m., after she got home from her work trip just before 2 a.m., and he told her he wanted to separate, the arrest affidavit alleges.

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Shanann Watts (right) and her daughters

Chris said that while he and Shanann “were emotional,” the conversation was “civil,” according to the affidavit.

Speaking with authorities later, Chris again said that he saw Shanann on Monday — this time around 4 a.m. — and “informed her he wanted to go through with a separation and they were both upset and crying,” police said in the arrest affidavit.

Chris claimed Shanann “told him she was going to a friend’s house that day.”

Video: Husband Who Made Emotional Appeal Accused of Murdering Family

Finally, in another police interview, after law enforcement allegedly uncovered the affair and after he asked to speak with his father, Chris said he would “tell the truth.”

He contended that he and Shanann had in fact talked about him wanting to separate after she got back from her trip early Monday but then he “walked downstairs for a moment” and when he got back to their bedroom he saw, via a baby monitor, that daughter Bella was “sprawled” and “blue” on her bed — apparently already dead — while Shanann was allegedly “actively strangling Celeste,” the affidavit states.

RELATED VIDEO: Pregnant Mom & 2 Daughters Likely Killed at Home — Allegedly by Husband — Before Bodies Were Dumped

Chris Watts (left) after his arrest

At that point, Chris claimed, he “went into a rage and ultimately strangled Shanann to death” before loading “all three bodies onto the back seat of his work truck,” according to the affidavit.

He then allegedly took them to an oil site owned by the company he was working for (he has since been fired) and then buried Shanann and hid his daughters’ bodies in oil tanks, where they stayed for roughly four days.

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Causes of death in the three killings have not yet been released. Authorities have not confirmed their suspected motive, though in charging Chris with murder they dismissed his account of what happened.

He is next set to return to court on Tuesday. He has not entered a plea and his public defender has not responded to PEOPLE’s multiple requests for comment.

“It’s really sad. It’s beyond belief, really,” a friend of the couple, Kris Landon, tells PEOPLE. “And it makes you wonder about other people you know. If this couple who seemed so perfect was like this, what are the other couples like?”