Canton, Georgia (CNN) -- New details emerged Thursday in the brutal slaying of a 7-year-old Georgia girl, hours after an attorney for the suspect said his client would plead not guilty.
Seven-year-old Jorelys Rivera's mouth was duct-taped, and her hands and feet were bound with plastic ties, a source close to the investigation said.
Authorities have charged 20-year-old maintenance worker Ryan Brunn with killing Jorelys, who was last seen alive Friday near a playground at the apartment complex where he worked in Canton, Georgia. They found her mangled body in a trash compactor there three days later, the source said.
A court date for an arraignment has not been set. David Cannon Sr., one of Brunn's court-appointed attorneys, said his client will enter a "not guilty plea" at the appropriate time.
Brunn wore an orange jumpsuit and a bullet-proof vest Thursday during his first court appearance.
His hands and feet were shackled during the hearing, which lasted only a few minutes.
After the hearing, defense attorney Daran Burns told reporters that his client was "very shaken."
"We're investigating our case," Burns said. "It's obviously a very tragic case. It's a very serious case. We take it very seriously. Just give us time to do our jobs."
After Cherokee County Superior Court Judge Frank Mills read him his rights Thursday, Brunn said he understood what he was being charged with and was satisfied with his counsel.
Brunn, who was arrested Wednesday, is in segregated confinement in prison and wore a bullet-proof vest Thursday due to the nature of the case, said Lt. Jay Baker, a spokesman for the Cherokee County Sheriff's Office.
"It's been a hot issue in the community. We didn't want to take any chances," Baker told reporters.
Jesus Palomino, who lives in the apartment complex, said he attended Thursday's court appearance "to see justice be served against this criminal that was living in my neighborhood."
"The mood right now inside the apartment complex is very saddening, you know, it's hard to go outside without looking both ways before you even step outside your door, because you're just scared that somebody might be there," he said.
Thursday's court appearance came after the little girl's mother called for capital punishment for the suspect.
"I don't want any charges brought against him," Joseline Rivera told CNN affiliate WSB. "What I want is the death penalty. He's an animal. He killed my little angel."
Brunn has not made a public statement, but his adopted brother has said he is innocent.
The warrant for Brunn's arrest charged him with murder and making false statements to law enforcement.
"The accused did unlawfully and with malice aforethought cause the death of Jorelys Rivera by hitting her on the head with a blunt object," it said.
Authorities have said there will likely be other charges, including kidnapping and sexual molestation.
The little girl's father, Ricardo Galarza, lives in Puerto Rico. He told CNN on Thursday that he last saw his daughter two years ago when she visited for the summer. She was supposed to visit for Christmas this year, Galarza said.
He echoed Rivera's call for the death penalty.
Meanwhile, a judge ruled that Joseline Rivera's two younger children -- Jorelys' half-siblings -- could return to the custody of family members, attorney John Connley told reporters.
Authorities took away the two children, ages 4 and 1, on Saturday, a day after Jorelys went missing. The Georgia Division of Family and Children Services cited lack of supervision. Connley, who represents the children's father, did not specify which parent would have custody.
A family friend said the father of the two younger children lives in Miami.
Authorities said Brunn has no known criminal history.
His adopted brother, Connor, told CNN affiliate WXIA-TV that the arrest was a "big mistake."
"I honestly think he is innocent. There's just no way he would do something like this. He's just a kind-hearted person," Connor Brunn said.
He has spoken with Ryan, he said, who told him "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.
On what friends say is Ryan Brunn's Facebook page, he described himself as being "very outgoing" and having "a 'wonderful' life, family, and friends."
In July, he posted a message slamming Casey Anthony, who was acquitted of killing her daughter in Florida. He wrote that Casey Anthony should have died, "but really she'll get hers."
Tips from the public led investigators to Brunn, who had been working at the complex since November 7, authorities said.
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.
Neighbor Heather Johnson-Coker said residents were suspicious of 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 said Wednesday.
Connor Brunn said investigators should have focused on the complex's other maintenance workers, who also had access to the trash compactor, instead of his brother.
"I think they were looking at him because he was one of the maintenance guys there," he said. "But he's just one out of what, four or five other maintenance guys that work there?"
Brunn was one of hundreds of people whom investigators interviewed in their search for suspects, Keenan said Wednesday.
"We're confident that Brunn is a killer," Keenan charged, 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," he added. "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."
CNN's Gustavo Valdes, Holly Firfer, Mike Brooks and Rich Phillips contributed to this report from Canton. CNN's Catherine E. Shoichet contributed from Atlanta.