The body of a man wanted in the slaying of his 8-year-old adopted son was found early Saturday on a farm in western Illinois, ending a three-state manhunt, police said.

Douglas Paul Maring, 30, was found in a farm building near Galena after the owner of the property reported finding a car believed to have been stolen by Maring, according to a statement from the Jo Daviess County sheriff's office.

The sheriff's office said it wouldn't release information on the cause of Maring's death until after an autopsy.

Authorities said Maring left a residence in Dubuque, Iowa, with 8-year-old Anthony Maring on Tuesday. Dubuque police received a call from the boy's mother, Heidi Maring, around midnight saying he was threatening to kill their son and commit suicide.

The boy, who had suffered a knife wound, was found early the next morning in a pickup truck that Maring crashed north of Galena while being pursued by police.

Illinois State Police Lt. Jim Winters said the boy's knife wound was inflicted before the crash. Anthony died a short time later at a hospital.

After the crash, Maring escaped on foot and apparently stole another vehicle, authorities said.

State police, county and local authorities from Jo Daviess and surrounding counties in Illinois, Iowa and Wisconsin had been involved in the search.