GREELEY, Colo. -- Weld County District Attorney Michael Rourke spoke before the court at Christopher Watt's sentencing Monday in Greeley.
Christopher was sentenced to live in prison without the chance of parole for the murders of 34-year-old Shanann and the couple's two daughters, Bella, 4, and Celeste, 3.
Rourke spoke for about 13 minutes. He said the reasoning behind the crime are still unclear to all but Christopher.
"I don't suspect that he'll ever tell the truth about what truly happened or why. Even if he did, there is no rational way that any human being could find those answers acceptable responses to such horrific questions," Rourke said.
The DA said Christopher's actions were calculated and did not occur during a "fit of rage."
Rourke said after Shanann returned home from Phoenix early Aug. 13, they had an "emotional conversation." While it is unknown what was discussed, Rourke said it is clear that Christopher strangled her.
The autopsy report says Shanann -- who was pregnant with a boy named Nico -- died from asphyxiation due to manual strangulation. Both Celeste and Bella died from asphyxiation due to smothering.
"The man seated to my right smothered his daughters. Why? Imagine the horror in Bella's mind as her father took her last breaths away," Rourke said, going on to explain that Bella tried to fight back.
"She fought back for her life as her father smothered her," Rourke said. Celeste, who was also smothered, did not have any external injuries.
Rourke then explained that Christopher methodically loaded the bodies into his work truck before disposing of them. Shanann was buried in a shallow grave in a remote area. Celeste and Bella were placed in crude oil containers.
"His motive was simple, your honor: He had a desire for a fresh start. To begin a relationship with a new love that overpowered all decency and feelings for his wife, his daughters and unborn son," Rourke said, referring to Watts' mistress.