Ryan Brunn, who lived and worked at the apartment complex, was taken into custody Wednesday afternoon on a murder warrant, said Georgia Bureau of Investigation Director Vernon Keenan.
Jorelys Rivera was last seen Friday evening leaving the playground to walk back home to get drinks for her friends. Authorities said she was taken to an empty apartment in the complex, where she was sexually assaulted, stabbed and beaten to death.
Keenan said Brunn, who has no known criminal record, had keys to both the empty apartment and the trash compactor bin where Rivera's body was placed.
"We are confident that Brunn is the killer and that is why he is in custody," Keenan said, declining to detail what evidence investigators have against him.
It was not immediately known whether Brunn had an attorney. He was being held at the Cherokee County jail.
Brunn is not a registered sex offender in Georgia, according to state records online.
Keenan said investigators focused on Brunn after receiving information from the public. Brunn had been under police surveillance since Tuesday night. Keenan said the investigation will continue for several months.
"This is a mammoth case," Keenan told reporters at a news conference in Canton. "We believe that this horrendous crime was planned and calculated, and we've recovered a lot of evidence."
Blue Ridge District Attorney Garry Moss said he had not made a decision yet on whether to seek the death penalty.
On Wednesday, Canton Police Chief Jeff Lance thanked investigators and volunteers who searched for the slain child.
"Our goal was to make an arrest for what has happened to this sweet, innocent little girl," Lance said.
When Rivera's body was found three days after she disappeared, the community where neighbors said they all knew each other was shaken and a makeshift memorial took root at the playground.
Investigators said they received numerous tips from the public and that valuable evidence had come from apartment complex residents. They also interviewed several sex offenders living at the complex, Keenan said. On Tuesday he said officials had no reason to believe those sex offenders were involved.
As details of the crime emerged, residents said they were worried.
"I'm very concerned," Drew Baucom, 17, said soon after the killing. "It makes me feel like my home life is violated, that I can't trust somebody walking around that you think you may know, but you really don't. It just worries me that something else will happen like this."
About 65 local, state and federal investigators worked the case and several hundred interviews were conducted, authorities said.
Jeremy Gibson, 24-year-old resident of the apartment community, said before the arrest that he was concerned about the safety of all the children who live there.
"Every day children play out here," he said. "It's starting to become a dangerous place for them. If it's happened to one little girl already, it could happen to someone else. I hope they catch whoever did it soon."
The manager of the apartment complex did not immediately reply to a message from the AP seeking comment.