Before her murder, Shannan Watts strongly suspected killer husband Chris Watts was cheating

The Colorado woman murdered by her cheating husband strongly suspected he was having an affair in the weeks before she and her young daughters were killed — and she was right.

On Monday, Chris Watts was sentenced to three lifetime prison terms without the possibility of parole after he pleaded guilty to killing his pregnant wife Shannan Watts and their daughters Bella, 4, and Celeste, 3. The autopsy reports obtained by CrimeOnline following the sentencing revealed that Shannan was strangled and Bella and Celeste were both smothered to death before Chris Watts disposed of their bodies on a property belonging to a petroleum company where he worked until his arrest in August, two days after his family disappeared.

People magazine reports that Shannan suspected Chris was having an affair, which has since been confirmed my his mistress — a co-worker who had only been involved with him since earlier this past summer, and reportedly believed he had finalized his divorce.

According to People, Weld County District Attorney Michael Rourke said at a press conference following Monday’s sentencing that Shannan was alerted to credit card charges made by her husband at restaurants near their Frederick home while she was visiting her family in North Carolina. The charges reportedly suggested he was not alone.

“We know she confronted him about that numerous times,” Rourke reportedly said. “We know that he was never completely forthcoming with her.”

Though Shannan correctly suspected an affair, the pregnant mother of two still tried to save her marriage — but her husband was reportedly unreceptive.

 “While Shanann texted the defendant over and over again in the days and weeks leading up to her death attempting to save her marriage, the defendant secreted pictures of his girlfriend into his phone and searched and texted her at all hours of the night,” Rourke said in court on Monday, according to People.

Prosecutors reportedly believe Watts murdered his wife and daughters on August 13 because he wanted a fresh start with his girlfriend, Nichol Kessinger, though she later said in an interview with the Denver Post that they had not discussed future plans. After Shannan and her daughters disappeared, Kessinger realized that Watts had been lying to her about his marriage, and went to investigators about their relationship and with her suspicions he may have been involved in their disappearance the same day he was later arrested.

Watts’s guilty plea meant that he was spared the death penalty.