Officials said McLellan will have his first court appearance at 9 a.m. Monday.
Aguilar's funeral is set for Saturday in Lumberton.
Fairmont police said that on Oct. 15, McLellan pointed a gun at a woman, tried to take her car, and demanded money. He left the scene without hurting the woman. Officials said he turned himself into police Nov. 13, eight days after Aguilar was kidnapped.
A body found in Robeson County was preliminarily identified as Aguilar, investigators said Nov. 27, ending a three-week search involving hundreds of investigators.
“We are absolutely devastated. I wish we had a different outcome for Hania’s family, for the community and for the hundreds of law enforcement officers and searchers who put everything they had into finding her alive,” Lumberton police Chief Michael McNeill said at a news conference.
McNeill told reporters that state crime lab tests indicate the body found was Hania. While a final determination will be made with dental records, investigators believe the body is hers.
"This is the outcome that we all feared," he said. "We did not want to hear this. We wanted to bring Hania back home and bring her back home alive to our community. It hurts."
The chief said Hania's body was found in a body of water in Robeson County about 10 miles south of the mobile home park where she was kidnapped Nov. 5 after going outside to start a relative's SUV before school.
Authorities wouldn't elaborate on whether the body had been concealed, but said it was not visible from the road or obvious to people passing by. Investigators spent Wednesday combing the area in daylight after finding the body the previous night.
The cause of death hasn't been released, pending an autopsy. Investigators would not describe the condition of the body. An FBI official said he did not have any information as to whether Hania was killed where she was found or elsewhere.
Police said a man forced Hania into an SUV and drove off. The SUV was found several miles south of her mobile home park. The body was found a few miles farther away.
McNeill has previously said that a witness saw a man dressed in black with a yellow bandana grab Hania in the Rosewood Mobile Home Park in Lumberton. Police said the eighth-grader had taken her aunt's keys to start the vehicle to prepare to leave for the bus stop. They say the man forced her into the green Ford Expedition and drove off.
The FBI soon joined the search, offering reward money and transmitting her picture around the country. The SUV was found abandoned several days later, but signs of the girl or her remains eluded investigators for several weeks.
Aguilar's mother and other family members gathered at the Lumberton Police Department Tuesday night, waiting on developments in the case. Her mother, visibly distraught, was led away in an ambulance. The FBI said that the last three weeks have taken a toll on the family.