(CNN) -- What sounded like the most tragic of accidents -- a dad absentmindedly leaving his toddler in the car on a scorching Georgia day -- is now being treated by police as a horrific, and intentional, crime.
New details from a Cobb County criminal warrant allege that Justin Ross Harris, 33, placed his son, 22-month old Cooper, into a Hyundai Tucson after eating at a fast-food restaurant. He then drove to his workplace a half-mile away, according to the warrant.
Harris returned to the car during his lunch break, opening the driver's side door "to place an object into the vehicle," the warrant states.
The boy was in a rear-facing car seat in the center of the Tucson's back seat, the warrant says.
Later that afternoon on June 18, around 4:16, Harris left his workplace near Vinings outside Atlanta. Minutes later, he pulled into a shopping center asking for assistance with the toddler, who had been in the car for about seven hours at that point, the warrant says.
The average temperature was about 80 degrees that day, but the mercury topped 92 at the hottest point in the day. Police say the temperature was 88 degrees when the child was pronounced dead at the scene.
At first, it seemed like a mistake. Witness Dale Hamilton told CNN affiliate WSB-TV that an emotional Harris pulled into the shopping center after purportedly realizing he had forgotten to drop Cooper off at day care at 8:30 a.m.
"Laid his son on the ground, started doing CPR trying to resuscitate him. Apparently the child wasn't responding," Hamilton told the station.
Police saw a crowd, and when officers began to investigate, they saw the child on the ground. Once it became clear that Cooper was dead, Harris had to be physically restrained, police said.
"There were a number of witnesses -- passers-by in the area who observed basically the father in a very distressed moment," said Sgt. Dana Pierce of the Cobb County police.
Added Hamilton, "He kept saying, 'What have I done? What have I done?' And that's all that I could ascertain that he was saying."
Police seemed sympathetic at first, and Pierce told media that Harris apparently forgot the child was in the back of the vehicle while he was at work.
When Harris was charged with felony murder and child cruelty, there was vigorous debate over whether the heartbroken father should be punished. Surely, he had suffered enough, many thought.
Erin Krans of Marietta started a change.org petition asking Cobb District Attorney Vic Reynolds to drop the charges. It garnered hundreds of signatures.
"This could happen to anyone. Anyone. Charging a grieving father is abusive," wrote Susannah Waldron of Universal City, Texas.
Another signatory, Molly Greenwood of Centerville, Ohio, wrote, "I think the accident alone is enough punishment for the man. I cannot imagine."
But the story of the hapless father making an innocent mistake quickly changed.
"Within moments of the first responders getting to the scene and doing their job and questions began to be asked about the moments that led up to their arrival at the scene, some of those answers were not making sense to the first responders," Pierce said.
"I've been in law enforcement for 34 years. What I know about this case shocks my conscience as a police officer, a father and a grandfather."
Last week, Harris pleaded not guilty to felony murder and child cruelty charges. He's being held without bond at the Cobb County Jail and is scheduled to appear before a county judge July 3.
Cooper's mother, Leanna Harris, told CNN last week that she's been advised not to discuss the case with the media.
"We have been in communication with the mother throughout the investigation. At this time, I'm not at liberty to discuss her involvement. That's a part of the case our detectives are working on," Pierce said.
Cobb County Medical Operations Manager Mike Gerhard confirmed that the autopsy of the child is complete, but the boy's manner of death has not been released.
Repeated calls to the defendant's attorney have not been returned, and a woman answering the phone at H. Maddox Kilgore's office said the lawyer would not be commenting at this time.
Cooper Harris' funeral will be Saturday at the University Church of Christ in Tuscaloosa, Alabama. The service is open to the public.