The Colorado man who pleaded guilty to the murder of his pregnant wife and two young daughters last year has given investigators new details of the killings.

Christopher Watts, 33, provided the information in additional interviews with authorities Feb. 18, according to NBC-affiliate station KUSA in Denver. Written notes and audio files are expected to be released next week as a part of the Colorado Open Records Act, KUSA reported.

Shanann Watts, 34, was found dead in mid-August in a shallow grave on the property of Anadarko Petroleum, where her husband worked. She was 15 weeks pregnant at the time with a boy the couple planned on naming Nico. The bodies of their daughters Bella, 4, and Celeste, 3, were discovered inside oil tanks on the petroleum company property.

When his family was first reported missing from their home in Frederick, north of Denver, Watts publicly pleaded for their safe return, telling reporters that he was "torn up inside" and he wanted "everybody to just come home."

Police said in an unsealed affidavit that they later learned Watts had an affair with a co-worker and lied about it to investigators.

According to the affidavit, Watts then changed his story by saying that he "strangled Shanann to death" after seeing her kill Bella and Celeste. He then directed authorities to the location where the bodies were buried.

Watts pleaded guilty to murdering the entire family in November and was sentenced to three consecutive sentences of life in prison with no possibility for parole as part of a plea deal to avoid the death penalty.