An autopsy will be performed Friday on the body of a 6-year-old Georgia boy who was found in a trash bag not far from his home.

Officials at the Georgia Bureau of Investigation's Crime Lab in Savannah will conduct the autopsy on Christopher Michael Barrios, who had been missing for a week in coastal Georgia before being found about three miles from his Glynn County trailer park on Thursday. His body was found by state game wardens stuffed in a plastic trash bag in a field near the Brunswick, Ga., airport.

Glynn County Police Chief Matt Doering said it was obvious the child had been slain, but would not say how. He escorted the boy's father, Mike Barrios, to the scene where Christopher was found, though Barrios did not actually view the body.

"That's the hardest time I've had to hold my composure," Doering told reporters when asked what it was like to break the news to the father. "That was the hardest part ... When it's your only son that has been killed and you want to go look for the last time, that's tough."

Doering said he expected to file murder charges against four people already in custody: George Edenfield, a 32-year-old convicted sex offender; his parents, David and Peggy Edenfield; and, family friend Donald Dale. The Edenfields lived in a trailer directly across from the Barrios family.

"We believe they did it," Doering told reporters, adding that he knew the motive for the killing but would not reveal it.

Edenfield told investigators he played a role in the boy's abduction. He was charged with violating his probation from a 1997 child molestation conviction, which prohibited him from contact with children under 18.

Christopher went missing just yards from his house last Thursday after playing alone on a nearby swing set. His family was never considered suspect in the case. Hundreds of volunteers aided the search as police chased down false leads provided by the suspects in custody.

"You suspected all along in your heart, it's just not the outcome you want," said volunteer searcher Mari Charnock, who dabbed at tears after the boy was found dead. "At least we know, though. At least it's over."

Many of the volunteers, several wearing T-shirts printed with the boy's photo, hugged and sobbed as Doering broke the news.

Cpl. Jesse Cook of the Department of Natural Resources and his colleague, Sgt. John Harwell, were aiding in the search and spotted tire tracks on the road curving off toward the tree line. They pulled over and saw the trash bag among the trees and brush about 15 feet from the road. They alerted detectives when they got close enough to notice flies and a strong odor coming from the bag.

"It was obvious," Cook said. "But if you weren't looking for it, you probably would've thought it was just a trash bag."

Christopher's uncle said now that a body has been found, the boy's family now at least can try to find some closure to their tragedy.

"It's a big relief, really, to know the boy is found, even though he's dead," Carlos Barrios told local FOX affiliate WAWS. "At least now he can get a proper burial."

Carlos Barrios said his family is "pretty torn up right now" and thanked all the volunteers and authorities who helped in the search.

Police said four shovels were found during the investigation: One was found Monday night during a search of George Edenfield's home, while the other three were found Wednesday night around Dale's home, Doering told FOX affiliate WAWS.

The Edenfields and Dale had been providing investigators with false information and leads for several days, police said.

"My hopes jumped back up that he's alive and that we're gonna find our baby alive and he's gonna come back home," Christopher's grandmother, Sue Rodriguez, told FOX News just hours before the tragic news of her grandson's death surfaced.

"They haven't found no baby's body and as along as that's not so, I'm gonna continue to hope and pray that he's alive and that he's coming home."

George Edenfield's parents and Dale were arrested this week and charged with obstructing an officer, providing false information and concealing the death of another — meaning they gave leads to police about where Christopher's body was that never panned out.

In one interview, police said George Edenfield told them he knew where the boy was, but in another he said he didn't know anything about his disappearance.

"The father and his friend basically confessed to burying little Christopher," Glynn County Police Capt. Jim Nazzrie had told FOX News. "They took us to the area, several areas … for some reason they want to lie about it, they can’t remember where they buried the body or if they did bury the boy," he said.

"[George Edenfield] actually said that he had hurt the boy and his momma and then had moved the boy," Nazzrie said.

Doering said Thursday that even though many leads the Edenfields and Dale gave police didn't turn up a body, the clues still were somewhat helpful. The body was not found in any of the places the suspects revealed to police, so they expanded their search, and that's what led them to the body.

"Everywhere we searched, we found nothing we were supposed to find," Doering said. But "we were confident that to some degree, they were telling us the truth ... that kept us looking, kept us focused."

Christopher was last seen last Thursday night walking on a road not far from the homes of his father and grandmother, who live in a mobile home park about a half-mile from Interstate 95 just outside the port city of Brunswick on the Georgia coast.

On Monday, the Georgia Bureau of Investigation issued a Levi's Call, the state's equivalent of an Amber Alert.

FOXNews.com's Liza Porteus and The Associated Press contributed to this report.