Christopher Watts, the Colorado man who killed his pregnant wife and their two daughters in August, was sentenced Monday to life in prison without the possibility of parole.

Watts received three consecutive life sentences on Monday after pleading guilty earlier this month to murder charges in the deaths of his wife, Shanann Watts, and their children, Bella, 4, and Celeste, 3. The plea deal also included one count of unlawful termination of a pregnancy, for the death of the couple's unborn child, and three counts of tampering with a deceased human body.

Prosecutors did not seek the death penalty in exchange for Watts’ guilty plea.

"I could objectively say this is perhaps the most inhumane and vicious crime that I have handled out of the thousands of cases I have seen. Nothing less than a maximum sentence would be appropriate," the judge said.

Shanann Watts’ mother, father and brother spoke in court during the sentencing, along with Christopher Watts’ parents. Shanann's father, Frank Rzucek, labeled his son-in-law a "heartless monster."

“You may have taken their bodies from me, but you will never take their love from me,” said Rzucek. “You monster thought you would get away with his. I don’t know how. The cameras do not lie. You carried them out like trash. Yes, I’ve seen the videotape.”

Shanann's brother, Frank Rzucek Jr., added: "There isn't a day that goes by that I don't cry for my family. They were my whole world. Why would you do this?...What kind of person slaughters the people that love them the most?"

Shanann Watts was reported missing Aug. 13 when a friend couldn’t reach the pregnant 34-year-old and she missed a doctor’s appointment. The two children were also nowhere to be found at the family’s home in Frederick, a town north of Denver.

Meanwhile, Christopher Watts appeared on local television pleading with the public for his family’s safe return. He was arrested in their murders days later when authorities recovered the girls’ bodies, which were submerged in an oil tank located where their father worked. Shanann Watts was buried in a shallow grave.

Watts later claimed to investigators he killed his wife in “a rage” when he discovered she had strangled their two daughters after he told her he wanted to separate.

Prosecutors have since called Watts' account "a flat-out lie."

Prosecutors said Watts smothered his daughters to death and that Bella had “fought back for her life.” He then strangled his wife.

The Associated Press contributed to this report.