Jason Karels pleaded guilty, but mentally ill, to the murders in December, according to the Lake County (IL) State's Attorney's Office.
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Statements from the children's family were read in court, describing them as innocent young lives who did not deserve what Karels did to them.
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Judge Booras accepted the negotiated sentencing and described Karels' actions as "sickening" and "despicable."
Prosecutors said he drowned the children - ages 2, 3 and 5 - in June of 2022. Their mother found the bodies at Karels' Round Lake Beach home.
Officers said Karels wrote a note reading, "If I can't have them, neither can you."
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Chief of the Domestic Violence Division Eric Kalata described Karels' actions as "brutal, evil, and sinister."
Karels had previously pleaded not guilty to the murders before changing his plea.
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