The child was accidentally left in the vehicle outside the family home in Harris County for several hours, the local sheriff said, as temperatures outside rose to 100 degrees. The boy’s mother had returned home with her two children in the back seat of her car when she saw her 8-year-old jump out and assumed her youngest child was gone, said County Sheriff Harris Ed Gonzalez. She realized two to three hours later that she was missing and ran outside to find her son tied to a child safety seat in the back of the car. The EMS was called and the young boy was found dead at the scene. The family was busy preparing for the 8-year-old’s birthday party at the time of the little boy’s death. The mother told police that her son usually knows how to get out of the car, but the car in which he died was a borrowed vehicle, Gonzalez said. Police said the investigation is ongoing. The family did not realize the absence of the 5-year-old until two or three hours later.FOX26 The day after the boy’s death, Harris County Sheriff’s Office posted tips on Twitter to teach kids car safety – including teaching them how to unlock their seat, honk, unlock hazards and unlock the front doors. The advice came with the note that this month is well on its way to being the hottest June in history. The 5-year-old is the fifth child in the US to die of heatstroke after being left in a car this year, according to meteorologist Jan Null, who has been tracking such deaths since 1998. His death is also the second such fatal incident in less than a week. Last Thursday, a 3-month-old baby died after being left in a hot car for several hours in Pennsylvania. The temperature in a car can reach 115 degrees when the outside temperature is just 70 degrees, according to the National Highway Traffic Safety Administration. Since 1998, 912 children have died in hot cars. In most cases, they were forgotten by a parent or caregiver.