Police in Florida said a father opened his truck after being at work for several hours to discover his 9-month-old daughter inside the truck and unresponsive.
"We received a call around (4:45 p.m.) of a child that was unresponsive and had been found in the back of a vehicle," said Lt. Donna Seyferth with the Rockledge Police Department.
Police said the infant was left strapped in her car seat inside her father's pickup truck that was sitting in the hot sun.
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Police said the girl's father arrived at work at the Fraternal Order of Police telemarketing office just after noon.
WFTV meteorologists said the temperature in that area of Florida at that time would have been around 89 degrees.
Witnesses told reporters that the child's father was supposed to drop his daughter off at daycare but apparently forgot.
Police said he discovered his daughter nearly five hours later. The man's coworkers heard him screaming and called 911.
"The child was unresponsive when the officers arrived. They took as many life-saving measures as they could. Ambulance and rescue did the same, but the child did not survive," said Seyferth.
Police say there are no obvious signs of foul play.
Police are still talking with the family and said it is too early to say whether criminal charges will be filed.
"I am ready to cry for these parents. It's hard," said Darlene Decker, who was one of several people who stopped by Monday night to drop off flowers and balloons at the site where the young girl died.