The Georgia Bureau of Investigation says Ryan Brunn, the man who pleaded guilty this week to killing 7-year-old Jorelys Rivera, hanged himself with his sweatshirt in his prison cell.

Details of the investigation and autopsy were released Friday afternoon, less than 24 hours after Brunn was found unresponsive in his cell.

"The ongoing investigation by agents from the GBI's Milledgeville Regional Office has not uncovered any evidence to indicate Brunn's death was anything other than a suicide," the release from the GBI's John Bankhead states.

Bankhead says they originally investigated whether he had been murdered, but there was no other trauma found to Brunn's body other than the ligature hanging.

He says Brunn gave no indication that he was thinking about killing himself.

"Agents interviewed him after he pled up in Cherokee County for a couple of hours," says Bankhead. "And he showed no signs whatsoever of being suicidal."

Prison officials said Brunn had been under suicide watch while at the Cherokee County Jail, not because he’d threatened to kill himself, but because deputies didn’t know anything about him and because the crime to which he confessed was so horrific.

But Bankhead and prison officials in Jackson refused to say whether they, too, had put Brunn under extra surveillance when he died.

Bankhead tells WSB's Pete Combs it's the first time in recent memory an inmate has killed himself so soon after arriving at the state prison.

Georgia Department of Correction Spokeswoman Kristen Stancil says Ryan Brunn was found unresponsive in his cell at 4:15 p.m. Thursday.

"He was pronounced dead at a local hospital at 5:37 p.m. of an apparent suicide," said Stancil.

Brunn, 20, pled guilty to the murder Tuesday and sentenced to life in prison. He was moved to the Georgia Diagnostic & Classification Prison in Jackson after the sentence.  Stancil declined to say if Brunn was being monitored.

Cherokee County Sheriff Roger Garrison told Channel 2 Action News that he had asked the DOC to give Brunn special treatment. Garrison said he was considered a “high risk inmate.”

Garrison also says Brunn had never attempted suicide while being held in the Cherokee Jail.

Brunn was a maintenance worker at the complex where Rivera lived. He admitted in detail in court that he lured the 7-year-old to a vacant apartment in an Atlanta suburb, molested her, stabbed her to death and then stuffed her body in a trash compactor.

That day, in a move that surprised even veteran law enforcement officials, he entered a guilty plea to Rivera's Dec. 2 killing at the complex in Canton where she lived and he had worked for about a month.

Reaction to Brunn’s death was swift and unforgiving.

“I wasn’t surprised, he’s a coward,” one caller to News/Talk WSB said. “You’re brave enough to take a child’s life and hurt that family. But you’re not brave enough as a man to go to a place where men are and get dealt with.”

“It’s not justice to me,” Devin Loop, who lives at the River Ridge Apartments where Rivera was killed, told Channel 2 Action News. “He got off easy. That poor little girl suffered. It was the coward’s way out.”

“As long as the family is happy with the outcome I guess the community can get back to the way it was before,” added River Ridge Apartment resident Chase George.

Oddly enough, Brunn's guilty plea was designed to spare him the possibility of being executed and save Rivera's family the emotional trauma of an extended trial. Vernon Keenan, chief of the GBI, also said the guilty plea gave his agents a unique opportunity to delve into the mind of a "cold and calculated killer."

After entering the plea, Brunn briefly apologized to the girl's family members, who sobbed quietly in the front row of the courtroom. He was swiftly sentenced to life in prison without parole.

The girl's mother, Jocelyn Rivera, said in a statement at the hearing she hoped Brunn suffered for his crime. After learning of his death on Thursday, she expressed relief.

"This is the kind of justice that I was expecting for him for all the damage that he made to my little daughter," Jocelyn Rivera said, according to The Atlanta Journal-Constitution. "Now, I can say that I feel satisfied."

Brunn's defense attorney, David Cannon, did not immediately return calls seeking comment. Cherokee County District Attorney Garry Moss also did not immediately return a call.

The case prompted the resignation of Canton police Chief Jeff Lance, after a scathing report found he took a "laid back" approach to the search for Rivera.