Canton, Georgia (CNN) -- The suspect in the slaying of a 7-year-old Georgia girl worked in the apartment complex where she lived, investigators said Wednesday.
Authorities arrested maintenance worker Ryan Brunn, 20, Wednesday afternoon.
He is charged with killing 7-year-old Jorelys Rivera, who was last seen alive Friday near a playground at the apartment complex in Canton. Investigators found her body in a trash compactor there three days later.
Tips from the public led investigators to Brunn, who had been working at the complex since November 7, authorities said.
"We believe that this horrendous crime was planned and calculated," Vernon Keenan, the director of the Georgia Bureau of Investigation, told reporters.
One resident said she told investigators about a recent conversation she had with Brunn, who mentioned that someone could break into one of the many vacant apartments in the complex and harm a child.
Jorelys was abducted "in the immediate vicinity" of the apartment complex's playground, then taken to an empty apartment nearby, Keenan said.
"We have evidence that the murder occurred in that vacant apartment," he said. "At some point, the child's body was then disposed of in the Dumpster and compacted into trash."
Authorities have said Jorelys died of blunt force trauma to the head, was stabbed and had been sexually assaulted.
Earlier, Keenan said investigators had found blood in an empty apartment.
Brunn's adopted brother told CNN affiliate WXIA that the arrest was a "big mistake," and said investigators should have focused on the complex's other maintenance workers.
"I honestly think he is innocent. There's just no way he would do something like this. He's just a kindhearted person," Connor Brunn told WXIA.
He said he'd spoken with his brother since the killing.
"He just told me he wouldn't touch a girl like that, he wouldn't ever do something like that. ... This is just all bogus. ... He knew that he was suspected but he never, like, thought that it would go to him. He was asked to help to go look for this little girl. And then he got brought into this," Connor Brunn said.
Neighbor Heather Johnson-Coker said residents were suspicious of Ryan Brunn after investigators found Jorelys' body in the trash compactor, which can only be operated with a key that employees at the complex have.
She said the maintenance worker had mentioned the large number of vacant apartments in the complex when a boy from the area went missing for a few hours recently.
"He said, and I quote, 'It would be really easy for someone to break in and do something to one of these children,'" Johnson-Coker told HLN Wednesday.
"I did talk to him on a daily basis and he seemed like a relatively nice guy. He wasn't socially awkward. He didn't seem to have any type of anger issue. He seemed like a regular, decent person who worked there to make a living just like anybody else," she said. "The statement at the time did not shock me. I did not think anything odd about it."
But Johnson-Corker said she told investigators about the conversation after investigators found Jorelys' body.
Days earlier, the maintenance worker was in a search party with her husband after Jorelys went missing.
"They were together searching not five feet from each other, and it just turns my stomach thinking about it," she said.
After Ryan Brunn's arrest Wednesday, mother Joselin Rivera wept next to a family memorial for her daughter, and said she didn't know if she would recognize the suspect.
"I can't tell you who he is. ... I don't want any charges brought against him. What I want is the death penalty. He's an animal. He killed my little angel," Joselin Rivera told CNN affiliate WSB.
She wore a T-shirt with Jorelys' picture that said, "We will always remember you."
Georgia Bureau of Investigation spokesman John Bankhead told CNN the 7-year-old's slaying was one of the most brutal crimes his agency has ever seen.
Ryan Brunn was one of hundreds of people investigators interviewed in their search for suspects, Keenan said Wednesday.
"We're confident that Brunn is a killer," Keenan said, but he added that the investigation will continue for months.
"We are investigating all of the past history of Ryan Brunn and piecing together what he's been doing the last several years," Keenan said. "We have sent agents to other states and also to other counties and we're going to backtrack all of his activities and make a determination if he has been involved in other crimes. He has no known criminal history to us, but we will find out."
Posts on a Facebook page that friends said belonged to Brunn recently talked of plans to move to Canton.
"New job,apt,life coming soon," an October 6 post said. A post on November 5 said, "Today is moving day! Not ready to go but i got to."
The brutal killing has shaken residents of the apartment complex, located about 40 miles north of Atlanta.
Residents shouted words like "monster" and "scum bucket" at Ryan Brunn as authorities arrested him Wednesday, neighbor Kelly Knight told HLN's "Issues with Jane Velez-Mitchell."
"It was very surreal. As soon as we heard they were coming in to that apartment, I went outside my door and I witnessed it all. And I even hollered at him that I'd like to shoot him myself," Knight said.
Ryan Brunn is scheduled to be arraigned Thursday at 1:30 p.m. at the Cherokee County Courthouse in Canton, Keenan said.
CNN's Gustavo Valdes, Holly Firfer, Mike Brooks and Rich Phillips contributed to this report from Canton, Georgia. CNN's Catherine E. Shoichet wrote the story in Atlanta.