A man who left a note to his estranged wife stating “if I can’t have them, neither can you”, has admitted killing their three children.
Jason Karels pleaded “guilty but mentally ill” on Friday to three counts of first-degree murder.
The 36-year-old will be jailed for life without parole, Lake County State’s Attorney Eric Rinehart said.
Karels admitted to killing five year-old Bryant Karels, Cassidy Karels, who was three, and Gideon Karels, aged two, by drowning them, in June last year.
When police arrived at the family home to check on the children’s welfare, they found the note addressed to his wife, Debbie Karels, prosecutors said.
Karels, of Round Lake Beach, Illinois, was arrested after crashing his car into a bridge on Interstate 80, in the town of Joliet, 73 miles (118 km) away, while trying to escape police.
He was injured in the crash and spent a short time in hospital.
Karels told first responders he was responsible for his children’s deaths and had tried to take his own life before fleeing the home, police said.
Officers found his blood in the house from his attempts to hurt himself.
Police said at the time of the deaths that the parents shared custody of the children but did not live together.
Mr Rinehart said in a statement: “This case has devastated the Round Lake Beach community and beyond. We hope that today’s resolution provides some measure of closure, and we will continue to provide support to the family.”