UPDATE: The autopsy on a 22-month-old left in an SUV determined the child died from hyperthermia and the manner is consistent with a homicide, Cobb County police said Wednesday afternoon.

Earlier story: An updated arrest warrant offers new details into the hours leading up to the death of a 22-month old toddler inside his father's SUV. The father and son stopped for breakfast on the way to work and the father returned to the SUV during the day, something he may not have told police.

A week after the boy’s death, questions linger regarding how his father could have forgotten he was in car seat for seven hours.

After the child died, Justin Ross Harris, 33, of Marietta, was charged with murder and cruelty to children in the first degree, according to Cobb County police. The first degree cruelty to children charge was downgraded Tuesday to second degree, according to a warrant released Wednesday. A first degree cruelty charge implies criminal intent. A second degree charge means investigators believe there was negligence, not criminal intent.

Hours before the toddler, Cooper Mills Harris, was pronounced dead, he and his father stopped at Chick-fil-A for breakfast, according to an arrest warrant obtained Wednesday by The Atlanta Journal-Constitution. The father then put his son back in a rear-facing car seat in the middle of the backseat and drove to work, less than a mile away, the warrant states.

When Harris got to work at a nearby Home Depot corporate office, he left the toddler in the backseat, the warrant states. Harris then went inside the building.

“During lunch said accused did access the same vehicle through the driver’s side door to place an object into the vehicle,” the warrant states. “Said accused then closed the door and left the car, re-entering his place of business.”

The warrant does not indicate what investigators believe Harris placed in the car and if he had any contact with the boy at that time.

At 4:16 p.m., Harris left work and drove about two miles to an Akers Mill Road shopping center, where he stopped and asked for help for the child. Bystanders attempted to revive Cooper, but it was too late. The toddler was pronounced dead in the parking lot.

Harris was handcuffed at the scene because he was not cooperating with investigators, police have said. He was arrested and charged about five hours later.

Harris remained Wednesday in the Cobb County jail, where he is being held without bond. His attorney declined to comment on the case Wednesday afternoon.

An autopsy has been completed on the boy, but those findings, including a cause of death, have not been released.

Previous story: The father of a 22-month-old toddler found dead in the back of an SUV on Wednesday knew the child had been left in the vehicle, a Cobb County public safety official told The Atlanta Journal-Constitution late Tuesday.

That information differs from Justin Ross Harris’ initial statements to Cobb police, including that he mistakenly left his son in his carseat while he went to work last week. Harris, 33, of Marietta, said he only realized the boy, Cooper Mills Harris, was in the backseat when he was driving away from his job at a Home Depot corporate office, police said at the scene.

On Wednesday afternoon, Cooper was pronounced dead in the parking lot of an Akers Mill Road shopping center, where Harris drove after noticing his son still strapped in to his car seat.

Earlier Tuesday, Cobb County police declined to discuss whether the investigation has expanded beyond the toddler’s father. But police say the investigation into Cooper’s death continues to evolve, and is far from over.

“This is a very active, very fluid investigation,” Officer Mike Bowman told The Atlanta Journal-Constitution Tuesday. “Our detectives have worked tirelessly to resolve the leads in this case. They are doing due diligence.”

It's been six days since Cooper was pronounced dead in a shopping center parking lot off Akers Mill Road. And the toddler's father, Justin Ross Harris, spent his sixth day Tuesday in the Cobb County jail, where he's being held without bond, charged with murder and cruelty to children in the first degree in connection to the child's death.

Police confirmed Tuesday that they are looking into possible inconsistencies into details provided by Harris late Wednesday afternoon, before Cooper’s body was removed from the scene. Specifics about what has changed and what investigators have since learned is not being released yet, Bowman said Tuesday.

“We know this is an emotional case,” Bowman said. “We know it’s weighing on heart strings.”

In other media outlets including CNN.com, Cobb police public information officer Sgt. Dana Pierce has said the case "shocks his conscience" as a police officer, but has declined to cite specifics.

The case has resonated with thousands of supporters who have signed a petition urging District Attorney Vic Reynolds to drop charges against 33-year-old Ross Harris. Contributions have hit more than $20,000 in support of the Harris family.

Still, police say they have probable cause to secure warrants against Harris, who was arrested within hours of his son being declared dead. Harris, employed by the Home Depot corporation in the IT department, initially told police he had forgotten to drop off Cooper before work.

Shortly after leaving work Wednesday, Harris said he realized his son was in the backseat of the Hyundai Tucson, still strapped into car seat, according to police. Harris said he then immediately pulled into a shopping center parking lot, where witnesses attempted to help revive the boy.

An autopsy has been conducted on the child, but the findings have not been released. Bowman said Tuesday he did not know when that report will be available.

Cooper’s mother, Leanna Harris, has declined to speak publicly about either the toddler’s death or her husband’s arrest.

The funeral will be held Saturday for Cooper, according to an obituary published Tuesday. The funeral for the toddler will be at 1 p.m. Saturday at the University Church of Christ in Tuscaloosa, according to an online obituary. A private family burial is planned.

— Christian Boone contributed to this report.