In a bombshell turn of events Tuesday, Chris Watts has reportedly reached a plea deal in the deaths of his pregnant wife, Shanann, and their daughters

In a bombshell turn of events on Tuesday, Colorado triple murder suspect Chris Watts pleaded guilty in the slayings of his pregnant wife and their young children in exchange for being spared a possible death sentence, PEOPLE confirms.

Watts, 33, was arrested on Aug. 15 and charged with murdering his wife of nearly six years, 34-year-old Shanann Watts, and their daughters, Bella, 4, and Celeste, 3.

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Shanann was about 15 weeks pregnant with a son at the time, and her family later said she planned to name Niko Lee.

In court on Tuesday, Chris pleaded to nine charges, according to prosecutors: five counts of first-degree murder, one count of unlawful termination of pregnancy and three counts of tampering with a dead body.

He will be formally sentenced to life in prison without the possibility of parole on Nov. 19. Prosecutors said later Tuesday that Chris’ defense team first approached them several weeks ago to discuss a plea deal.

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Shanann’s family was in court for his plea, according to local reporters. The district attorney’s office, in announcing Chris’ plea deal, said it had been reached with the consent of Shanann’s relatives.

Chris has been held at the Weld County Jail since his arrest.

The Case So Far

Shanann and her girls vanished after she returned home from a business trip in the early hours of Aug. 13.

In the ensuing days, Chris made a televised plea for their safe return, raising suspicions with his strangely calm — even stilted — demeanor.

Under later police questioning, Chris allegedly said he would “tell the truth” after investigators told him they found out he was having an affair with a co-worker, according to an affidavit supporting his arrest that was unsealed in late August.

Chris then admitted he killed Shanann after flying “into a rage” when, he claimed, he saw her strangling one of their daughters via a baby monitor after he had told her he wanted a separation, according to the arrest affidavit.

In pleading guilty on Tuesday, Chris essentially admitted that explanation was a lie.

“What I can tell you most affirmatively today, by what happened in the court room, is the spotlight that he tried to shine on Shanann falsely, incorrectly … has been corrected,” Weld County District Attorney Michael Rourke said at a news conference Tuesday.

“The spotlight shines directly where it belongs: on him.”

Rourke said that authorities have a “partial motive” in the triple murder but said he could not discuss it further until after Chris’ sentencing in two weeks.

The bodies of Shanann and her girls were found the day after Chris’ arrest on an oil site owned by the company where he was working and from which he has since been fired.

Shanann was buried in a shallow grave and their daughters’ bodies were hidden in nearby oil tanks, where they stayed for roughly four days, according to Chris’ arrest affidavit and other court filings.

Those who knew the couple said they seemed happy — until not long before the killings. One friend told ABC News that Chris had grown distant: “He wasn’t being the loving Chris that he normally was. He wasn’t touching or hugging or doing stuff like that.”

But family was everything to Shanann.

“That’s all she talked about,” Kris Landon previously told PEOPLE. “She talked about her girls as miracles, because she had some health problems and didn’t know if she’d have kids. But she really embraced motherhood, and I thought she embraced her marriage, too. They seemed like partners. Amazing partners.”

Chris in Jail: ‘Willing to Confront Reality’

Chris was previously on suicide watch in jail and asource who had contact with him told PEOPLE that he was despondent.

But, according to the same source, Chris’ demeanor changed dramatically in previous weeks. “He’s been more active,” the source says. “He doesn’t sleep all day away. He’s actively taking part in his own defense. He reads a lot, and has contact with his attorneys.”

“He’s actually very energized now,” the source continues. “He’s willing to confront reality now and to decide what his best move is. … He’s able to look at things logically now and make the right decisions for himself. He’s turned a corner.”

Of Chris’ decision to plead, the source explains: “Chris had to come to terms with reality. He didn’t like it at all, but he’s smart enough to know that his back was against the wall, and the best thing for him to do was to plead guilty.”

“The evidence against him was overwhelming,” the source says. “There was physical evidence and his own words that would convict him. His story didn’t work.”

Speaking Tuesday, prosecutor Rourke said Shanann’s family was processing a mixture of emotions — relief, “extraordinary sadness” — about the plea.