"We know you are at peace playing in heaven’s playground and are happy you no longer have to suffer," Crystal Lake Police Chief James Black said about Andrew "AJ" Freund.
Black said Andrew's parents, JoAnn Cunningham and Andrew Freund Sr., were interviewed by detectives and gave them information that led them to the shallow grave in Woodstock, about 20 minutes from the family's home in Crystal Lake.
The body was found wrapped in plastic; a cause of death is not yet known, Black said.
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Andrew's parents had told police they last saw him at roughly 9 p.m. on April 17. In a 911 call released by authorities Tuesday, the boy's father told a dispatcher that he had gone to a doctor's appointment on the morning of April 18 and when he returned to his Crystal Lake home, his son was gone.
"We've canvassed the neighborhood. I went to the local park, the local gas station down here where we sometimes take him to buy treats ... I have no idea where he would be," Freund said.
Police searched a park near the couple's house Tuesday and asked neighbors to turn over home surveillance videos. A canine team was also brought in and it picked up Andrew's scent at the family's house, indicating that he did not leave on foot, detectives said earlier in the week.
Freund and Cunningham are currently in custody and both face five counts of first-degree murder. Cunningham was also charged with four counts of aggravated battery, two counts of aggravated domestic battery, and one count of failure to report a missing child death.
Freund was also charged with two counts of aggravated battery, one count of aggravated domestic battery, two counts of concealment of homicidal death, and one count of failure to report a missing child death.
The day Andrew was reported missing, his mother was arrested on an outstanding traffic warrant stemming from a December 2018 incident for driving with a suspended license. According to the incident report, Cunningham drove to a nearby fast-food restaurant to have someone call the police to report an alleged burglary at her home.
In the report, Crystal Lake police officers expressed concern over the squalid living conditions at the home. One officer wrote that the house did not have an "acceptable standard of living" and said there was dog feces and urine inside. Several windows were broken and the fireplace did not appear to work, the officer wrote.
Another officer wrote that the house was "cluttered, dirty and in disrepair" and the smell of feces was "overwhelming." One of Cunningham's two kids also had a large bruise on his right hip, the officer wrote. The children were removed from the home and taken to the police station after Cunningham was arrested for driving with the suspended license. A child welfare worker interviewed the children at the police station, and released them back to Cunningham after she posted bond because they could not determine how the child got the bruise, the report states.
Police were called several more times to the family's home. In September 2018, an officer responded to the home after someone reported that the family had been living there without power. Cunningham refused to let police into the house but the officer noted in the report that both children appeared to be "happy and healthy."
Following Andrew's disappearance, his younger brother, Parker, was removed from the home. Parker, 4, is currently in the custody of the Illinois Department of Children and Family Services.
Minyvonne Burke is a breaking news reporter for NBC News.