(CNN) The body of a 5-year-old boy reported as missing last week was found wrapped in plastic in a shallow grave on Wednesday, and his parents have been charged with murder, police said.

Crystal Lake Police Chief Jim Black said police interviewed the parents of Andrew "AJ" Freund overnight after information was obtained through forensic analysis of their cell phone data.

The parents, Andrew Freund Sr. and JoAnn Cunningham, then provided information that ultimately led to the recovery of AJ's body in Woodstock, Illinois, about 10 miles from their home in Crystal Lake, police said.

They both face charges of first-degree murder, aggravated battery and aggravated domestic battery and failure to report a missing or child death, Black said. Freund Sr. also faces charges of concealment of homicidal death, police said.

The cause of death is unknown at this time.

"To AJ's family: It is my hope that you may have some solace in knowing that AJ is no longer suffering and his killers have been brought to justice," Black said.

JoAnn Cunningham and Andrew Freund Sr. are charged in the death of their son, AJ.

Cunningham's attorney has not responded to requests for comment. It is not clear whether Freund Sr. has retained legal counsel. They are expected in court Thursday for a bond hearing.

The search began last Thursday morning when his father calmly called police and reported him as missing.

"We have a missing child," he said, according to a 911 call released by the Crystal Lake Police Department on Tuesday. "Woke up this morning and he wasn't ... he wasn't."

Freund told a 911 dispatcher that he put AJ to bed in his pajamas last Wednesday night but could not find him in the morning before school.

"I had a doctor appointment this morning and when I got back from the doctor's appointment and I checked in on him to say good morning and he wasn't there," the father told the dispatcher Thursday.

He said he searched all around the house and canvassed the neighborhood but couldn't find him.

The resulting search has included 15 police agencies, drones, and rescue canine units. But police said it was likely that AJ had not walked away and was not abducted, and instead focused the investigation on the family home.

Sonar teams that searched Crystal Lake found nothing, and the canine teams "only picked up Andrew's 'scent' within the residence, indicating that Andrew had not walked away on foot," the police said.

"(T)here is no indication that would lead police to believe that an abduction had taken place," the department said in a statement.

In addition, Crystal Lake Police earlier said Cunningham "continues to be uncooperative with police."

Child welfare investigations

Police on Tuesday released 63 pages of reports detailing several police calls to Andrew's home in recent years. In December, for instance, an officer described unlivable conditions in the home with "dog feces and urine" scattered there.

The officer during the visit also reported a suspicious bruise on one of the children, but a child welfare worker was unable to make a determination of abuse, the report said. Someone at the house said it may have been caused by a dog.

Months earlier, a local resident called police to check on the children because the home had been without power for weeks, according to the reports. An officer wrote the two children appeared "healthy and happy" and that child welfare authorities said the lack of electricity did not warrant their investigation.

The Illinois Department of Children and Family Services has "been involved with the family" since AJ's birth, department spokesman Jassen Strokosch told CNN. AJ "was brought into care with us" soon after he was born, when "neglect was indicated on part of the mom," Strokosch said. From 2013 to 2015, the infant was in the care of someone else, he said.

The department was called in twice in 2018 on allegations of neglect in March and of abuse and neglect in December, Strokosch said. The allegations were determined to be unfounded in both instances, he said.

A younger sibling who had been in the home until this week is now living with another family, Strokosch said. The acting director of the department, Marc Smith, said the care and safety of that sibling is a priority.

"This news is heartbreaking. Protecting vulnerable children who come to our attention is at the core of our mission at DCFS. All of us feel this loss," Smith said.

Parents spoke to the media

Andrew Freund Sr. late last week spoke to TV cameras saying they were extremely worried about their son.

"AJ, please come home," his father said. "We love you very much. You're not in any trouble. We're just worried to death. Please, please come home."