The man suspected in the death of 11-year-old Audrii Cunningham is a family friend who was entrusted with taking her to the school bus on the morning she vanished – and later participated in the massive search for the girl before her body was found in an east Texas river, authorities said.

Audrii’s family thought the suspect, Don Steven McDougal, was just taking the girl down the street when the pair left her home Thursday morning, Polk County officials said. But she never made it onto the school bus or into her classroom, and a bag resembling her bright red Hello Kitty backpack was later found near a local dam.

Prosecutors are preparing an arrest warrant for McDougal, 42, and believe the evidence supports a capital murder charge, Polk County District Attorney Shelly Sitton said Tuesday.

Audrii’s body was found Tuesday in the Trinity River, downstream from the reservoir near where the backpack was found. It was one of several locations McDougal told investigators he had gone around the time of her disappearance, Sheriff Byron Lyons said.

Investigators located Audrii’s remains using cell phone records, video analysis and information from McDougal, Lyons said.

The condition of Audrii’s remains is not being released, the sheriff said, and the Harris County Medical Examiner’s Office will determine her cause of death.

To help uncover the body, Lyons said, water management authorities slowed the flow of water from the Lake Livingston reservoir – one of the largest reservoirs in the state, with 83,000 surface acres – allowing the river level to recede enough to reveal the remains.

“I express my deepest sympathies and condolences to everyone who knew, who cared for and loved Audrii,” the sheriff said. “We will continue to process the evidence that has been gathered to ensure justice for Audrii.”

The suspect is already in custody after being arrested Friday night on an unrelated aggravated assault charge, the sheriff’s office said.

CNN has been unable to determine if McDougal has obtained legal representation and has reached out to his family for comment on the accusations against him.

McDougal, a friend of Audrii’s father, lived in a trailer on the family’s property and sometimes took the girl to catch her school bus in the neighborhood, the sheriff said. He has been the main person of interest in her disappearance as authorities frantically scoured the rural east Texas town of Livingston – about 70 miles northeast of Houston, he said.

McDougal joined the search efforts and was seen knocking on neighborhood doors and asking if anyone had seen Audrii, the sheriff told CNN. But Lyons doesn’t believe his efforts were genuine.

“To me, it simply tells me is that he’s trying to give the appearances that he has no play or he’s not at fault in her disappearance and that (he’s) part of the concerned parties who were trying to locate her,” Lyons said Tuesday.

In the days after Audrii vanished, McDougal claimed in several social media comments that he was not guilty in her disappearance and has “done nothing wrong,” according to activity on a Facebook account appearing to belong to the suspect.

“I’m not guilty,” reads a comment from the account under a post on the Facebook page “True Crime Society” the day after Audrii was reported missing.

“I was there and was questioned. I am not running or hiding,” McDougal wrote before commenting again and saying, “I have done everything I can to help find her. I have done nothing wrong.”

CNN has sought comment from investigators about the Facebook comments.

Suspect has decadeslong criminal history

McDougal has a lengthy criminal history dating back to at least 2003, with convictions for violent crimes and one for enticing a child, according to court records in several Texas counties.

In 2007, he was convicted of enticing a child in Brazoria County, Texas. Court records show he pleaded no contest and was sentenced to two years in prison but was given credit for 527 days.

Online records do not detail the specific allegations in the child enticement case. But the offense is defined by the state as “the intent to interfere with the lawful custody of a child younger than 18 years” when a person “entices, persuades, or takes the child from the custody of the parent or guardian.”

McDougal was also convicted in 2010 and 2019 for aggravated assault with a deadly weapon.

The victim in the first aggravated assault case said McDougal, his former coworker, attacked him after being thrown out of his house.

“He showed up with some other friends that I had,” Elic Bryan told CNN on Tuesday.

McDougal started stabbing the door before coming back inside, Bryan said.

“He came at me with the knife, and I had my shotgun, and I hit him in the face with it,” Bryan said. “I had no idea he was that kind of person.”

That aggravated assault case led to a four-year prison sentence.

‘You are broken, you are mad, you are empty’

Audrii’s loved ones are now grappling with not just the agony of her death, but also the criminal investigation of a suspect once considered a family friend.

The fifth-grader’s classmates and teachers are also grieving, the Livingston Independent School District said in a statement on Facebook.

“While the details of this tragedy are still unfolding, our hearts go out to the entire community during this heartbreaking loss,” superintendent Brent Hawkins said.

During the dayslong search for Audrii, her mother said she understood the anguish of parents of missing children, whom she had only heard about on the news.

“There’s not words for it. There is not one feeling you feel. It’s a roller coaster. You are broken, you are mad, you are empty. And right now, I am empty,” Matthews told CNN affiliate KPRC on Friday.

“She has so many opportunities ahead of her, and she deserves every right to be able to reach those opportunities.”