FREDERICK, Colo. -- The parents of Shanann Watts defended their slain daughter on Tuesday, saying statements by the family of Christopher Watts were "vicious, grotesque and utterly false."
Christopher Watts pleaded guilty earlier this month to killing his pregnant wife Shanann and two children, 4-year-old Bella and 3-year-old Celeste.
On Monday, the family of Christopher Watts spoke about their son's guilty plea earlier this month, with his mother Cindy Watts saying she knows her son killed his wife, but she does not believe he killed his children.
"He did kill her, but the kids, no. It's very difficult, very difficult. I can't imagine my son doing that. He couldn't have done that," Cindy Watts said.
Cindy Watts said she knows her son should spend a long time in prison for killing his wife, but she claims he was stuck in a verbally abusive relationship.
On Tuesday, Shanann Watts' parents, Frank and Sandra Rzucek, responded to the statements made by Cindy Watts in comments released by the law firm representing them.
"Shanann Watts was a faithful wife, and the most gentle and loving mother in the world to her children Bella, Celeste, and Nico. She was also the best daughter any parent could ever hope for. Shanann was a wonderful soul.
"Everyone who knew Shanann knows this to be true. Even Chris Watts knows this to be true. Yet Chris Watts still chose to murder Shanann, Bella, Celeste, and Nico. Chris Watts still chose to dump the bodies of his own family in oil tanks. And Chris Watts still chose to lie about it until he could lie no more. He pled guilty to murdering his family because he is guilty.
"Monday evening, the parents of Chris Watts gave an interview in which they attempted to defend their son. In doing so, they felt the need to make vicious, grotesque and utterly false statements about Shanann. Their false statements, however hurtful and inaccurate, will never alter the truth about Shanann, and will never alter the truth about the crimes committed by their son, Chris Watts.
"Shanann’s memory and reputation deserves to be protected. And her family is fully prepared to do so."
Christopher Watts pleaded guilty to nine charges: 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.
According to an arrest affidavit, Christopher Watts was actively involved in an affair with one of his co-workers. He admitted to the affair at first, then denied it, according to prosecutors.
RELATED: Christopher Watts arrest affidavit
The arresting documents claim Watts caught his wife strangling their daughters to death after the couple had a conversation about them separating early in the morning of Aug. 13 in their Frederick home.
He claims he then strangled his wife “in a rage.” Watts told investigators he loaded the bodies into his work truck and buried them on property owned by his employer, Anadarko Petroleum.
Shanann Watts, who was 15 weeks pregnant, and her daughters were reported missing at 1:40 p.m. on Aug. 13.
The Colorado Bureau of Investigation issued a missing-endangered alert for the three the next day.
Christopher Watts said in a several interviews that he didn’t know where his wife and daughters were.
The body of Shanann Watts, 34, was recovered in a shallow grave near an oil tank.
Court documents said the girls were found in an oil well in close proximity to their mother’s body.
Court documents filed by defense lawyer James Merson said the girls had been submerged in crude oil for four days.