COBB COUNTY, Ga. -- A Cobb County man charged with murder and cruelty to children after leaving his 22-month-old son in a hot car for more than seven hours made his first court appearance on Thursday.

READ: Arrest warrant for felony murder charges for Justin Harris

Police are investigating how the boy, named Cooper, ended up in the back of 33-year-old Justin Ross Harris' vehicle. Harris initially told police he went to work at around 9 a.m. on Wednesday. He said he was supposed to bring the boy to daycare, but instead forgot and went to work.

The boy was strapped in his car seat in the back of the vehicle for seven hours as the temperature rose to 88 degrees.

Around 4 p.m., as he was driving home from work, Harris said that he noticed that his son was in the back seat and pulled over at the Akers Mill Square shopping center on Cobb Parkway. Harris tried to perform CPR on the boy, according to a witness, but the child was pronounced dead at the scene.

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Police filed criminal charges against Harris on Thursday as they investigate the circumstances behind the boy's death.

"Investigators are trying to really nail down...the sequence of events and how that happened," said Sgt. Dana Pierce of the Cobb County Police Department. "We have been in communication with the mother. We will continue that communication as well as our investigation."

Harris is being held without bond in the Cobb County Jail. He entered a not guilty plea in his first court appearance on Thursday night. A bond hearing was set for July 15.

Harris works for Home Depot. That company issued a statement on Thursday saying,

Like the rest of our community, we're deeply saddened by this tragic loss. We continue to work with authorities on their investigation and grief counselors are available for our associates who request assistance.

RELATED : Ga. launches "Look Again" campaign to keep children safe

Just weeks ago, a new campaign called "Look Again" was launched in Georgia. In the ad, state leaders and a the father of a 2-year-old heatstroke victim remind everyone to take the little bit of time to look again before you leave your vehicle. That means checking the front and back of your car and then, just to be sure, look again. Anyone who sees a child left alone in a vehicle is urged to call 911.ID=11004343