ATLANTA (AP) — The investigation of a toddler's death in a hot SUV in Georgia hinges on a key question: Was the boy the victim of a horrific accident after his father simply forgot to take him to day care, or did the man know the child was inside when he left him strapped in for seven hours?

A newly filed arrest warrant supporting the murder charge against the father states that 33-year-old Justin Ross Harris stopped with his son for breakfast and also returned to put something inside his vehicle around lunchtime while the child was inside it.

Harris has told police he was supposed to drive his 22-month-old son to daycare but drove straight to work on June 18 without remembering the boy was strapped in his seat until the ride home. After spending the day at work, he pulled into a shopping center parking lot and hysterically asked for help for his son.

Harris was being held without bond Wednesday. Jail records didn't list an attorney for him.

The new warrant filed late Tuesday also downgrades one charge Harris from first-degree child cruelty to second-degree child cruelty. First-degree cruelty to children requires a person to "maliciously" cause "cruel or excessive physical or mental pain," while second-degree cruelty to children is caused by "criminal negligence" under Georgia law.

Harris put the toddler in a rear-facing car seat in the center of the back seat of his Hyundai Tucson after eating at a Chick-fil-A restaurant the morning of the boy's death, the new warrant says. He then drove about 10 miles to work and left the child strapped into the car seat when he went inside, the warrant says.

At lunchtime, Harris returned to the vehicle and opened the driver's side door to place an object inside and went back inside his workplace, the warrant says. It does not explain how the officer knows that.

Around 4:15 p.m., Harris left work and, soon after, pulled over at a shopping center and asked for help with his child, the warrant says. The child was left in the vehicle for about seven hours, the warrant says. The temperature that day was 88 degrees at 5:16 p.m., according to the first warrant in the case, filed the day after the child died.

An autopsy has been completed but the cause of death hasn't been released. The warrant says Harris caused the child's death by leaving him in the hot car.

Prosecutors may opt for the harshest charges available and then scale back in felony murder cases, said Jessica Gabel, an associate professor of law at Georgia State University in Atlanta.

"They're definitely going to look at how healthy was the child, the family's previous history, whether dad was usually somebody who was very responsible," she said. "And the defense, if this reaches a trial, will be collecting their evidence that he was a good parent, a fit parent."

Neighbors and acquaintances of Harris and his wife described them as loving parents.

Their landlord, Joe Saini, told The Atlanta Journal-Constitution that the couple were "very, very nice" people who were in love with their baby.

"Everything was going right for this couple," Saini said. "They wanted to buy a house so they could have some space for their child to run around the backyard."

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