A Colorado man accused of killing his pregnant wife and their two daughters has reached a surprise plea agreement to avoid the death penalty, according to the Weld County District Attorney. 

Chris Watts pleaded guilty Tuesday to all nine counts he faced. Watts was arrested in August after killing his family and dumping their bodies on land belonging to an oil company where he formerly worked.

The bodies of the girls, Bella, 4, and Celeste, 3, were found in oil barrels, while wife Shanann's remains were discovered in a shallow grave nearby. Watts initially claimed he killed his wife in an act of passion after finding one daughter dead and Shanann trying to kill the other.

Watts, 33, had been charged with murdering his wife of nearly six years, Shanann, 34, and their two girls. He also was charged with first-degree unlawful termination in connection with their son's 15-week-old fetus of their son. 

Authorities have not disclosed the victims' causes of death. But a defense motion filed in August suggested the girls had been strangled, according to The Denver Post.

The three victims were reported missing on Aug. 13 by a family friend. Watts appeared on local TV pleading for their return on the day before he was arrested. He told police he had informed his wife he was leaving her. Investigators later discovered he had been having an affair with a coworker, authorities said. 

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