The Marietta dad charged with murder in his son’s death knew the toddler was locked inside his sweltering SUV well before he told police he first made the discovery, a Cobb public safety official close to the investigation has confirmed.

The revelation casts serious doubt on Justin Ross Harris’ claim that he he didn’t realize his son was still in the car until he drove away from his job at Home Depot’s corporate offices in Cobb County. Harris, 33, told police he had mistakenly left the 22-month-old in his car seat while he went to work.

The toddler was a regular at Home Depot’s child care facility, which is located across I-285 from where Harris is employed. It’s unclear where he was headed when he says he first discovered Cooper wasn’t breathing.

Cooper Harris was the 13th child killed this year after being locked inside a heated car. His death garnered worldwide headlines and furthered a national conversation among parents about whether anyone could be capable of forgetting about the whereabouts of their child for such a long period of time.

Witnesses in the mall parking lot where Justin Harris pulled over after presumably discovering his son’s still body heard him scream, “What have I done? What have I done? I’ve killed our child.”

But investigators apparently found evidence that Harris went to his car before leaving his office that day.

“This is a very active, very fluid investigation,” Cobb police spokesman 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.”

Bowman confirmed investigators are focusing on inconsistencies in Harris’ story but would not elaborate.

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

Cobb police have refused to reveal results of an autopsy performed on the toddler.

Justin Harris, an IT worker, remains in Cobb jail without bond, charged with murder and cruelty to children. He will not be allowed to attend his son’s funeral Saturday afternoon in Tuscaloosa, where the family lived until two years ago.

Police also remain tight-lipped about what prompted them to quickly bring murder charges against Harris, leading to a groundswell of support from friends and strangers alike.

As of late Tuesday afternoon more than 11,000 people had signed a petition urging Cobb District Attorney Vic Reynolds to drop criminal charges against Harris. And more than $21,000 has been contributed to a trust fund set up to help cover expenses brought on by Cooper’s death.

William Overstreet, who said he has known Harris for more than a decade, described him as a “selfless man who loved people and loved his family more. Nothing in his life even hints at this behavior.

“Please have mercy on a devestated father,” Overstreet, of Austin, Tex., wrote on the petition at change.org.

Another longtime friend, Matt Wiley, said Harris was being unduly punished.

“These charges are excessively punitive,” said Wiley, of Northport, Ala. “This was an accident, he has no criminal record and he is not a flight risk. This is a lynching and it needs to stop.”

When reached for comment Tuesday, Wiley said he had been asked by the Harris’ attorney to refrain from speaking to the media.

Cooper’s mother, Leanna Harris, has declined to speak publicly.