Police in Cobb County, Georgia, do not believe Justin Ross Harris left his 22-month-old son Cooper to die in the family's SUV by mistake, CBS News Correspondent Mark Strassman reports.
A new police warrant says last Thursday morning, Harris and his son ate breakfast at a Chick-fil-A. He strapped Cooper into a rear-facing car seat, and made the three-minute drive to his office at Home Depot.
Harris went inside -- and left the boy inside the closed SUV, instead of taking him to his regular day care.
Investigators say Harris returned to his SUV at lunch, opened the driver's side door, and put something inside. Then he went back to work.
Harris told police he was driving home from work when he noticed his son still strapped into his car seat. He pulled into the parking lot and tried without luck to revive the boy. Witnesses heard him cry several times "what have I done?"
By the time police got here, the little boy was dead.
Ralph Mickens, a pizza cook, heard the SUV screech to a halt. Harris needed help.
Mickens told CBS News: "There was a guy right there trying to give the baby CPR, and the father was pacing around hysterically, just saying 'why me? What happened?'"
The 34 year-old Harris has pleaded not guilty to murder, and more than 10-thousand supporters have signed an on-line petition to free Harris immediately. A video produced by his supporters calls the boy's death a terrible accident, nothing more.
Police insist the evidence points to murder.
"I'm a father myself," Mickens said. "I have a three-month-old girl at the house. Just to see something like that happen to a baby, whether accidentally or intentionally, it's pretty dramatic, man."
A coroner has ruled the boy died from hyperthermia, when the body's temperature rises and stays well above its normal temperature. The little boy will be laid to rest on Saturday. His father will not be allowed to attend.