(CNN) -- As police in Georgia investigated the death of a 22-month-old boy left seven hours in a sweltering SUV, they seized computers from the father's office, a source with knowledge of the investigation told HLN's Nancy Grace. The officers found something startling: an Internet search for "how long does it take for an animal to die in a hot car," the source said. Initially, police seemed sympathetic, describing the death of Cooper Harris on June 18 as the result of tragic absentmindedness. They said the dad had apparently forgotten the boy was in the back seat of his Hyundai Tucson; he didn't remember until he was done with his work day, drove a couple of miles, and pulled into a shopping center parking lot. But police became suspicious as they investigated. "The chain of events that occurred in this case does not point toward simple negligence and evidence will be presented to support this allegation," said Cobb County Police Chief John House. A criminal warrant released Wednesday described the events that led to Cooper's death. A timeline of events On the day Cooper died, June 18, Harris stopped for breakfast at a fast-food restaurant and afterward strapped his son into a rear-facing child restraint seat on his SUV's backseat, police said. He drove to his workplace, a Home Depot corporate office, about a half-mile away. He works as a Web designer there. Normally, he would take his son to an on-site day care. But that day, police said, Harris left him in the car seat. During his lunch break, he returned to his car, opening the driver's side door to put something inside, police said. After work, around 4:16 p.m., the 33-year-old father got in his car and drove away. A few miles away, he stopped the car at a shopping center and called for help. When it became clear Cooper was dead, Harris was so inconsolable police had to restrain him. "What have I done?" he wailed as he tried to resuscitate the little boy. It's unknown when the Internet search was conducted and whether the father did the searching. Police have declined comment when asked about the computer search. The father, Justin Ross Harris, was charged with murder and second-degree child cruelty. Police in Cobb County, just outside Atlanta, have been tight-lipped and haven't said if what they found on the computer is one of the reasons they arrested Harris.