HOUSTON -- A 3-year-old boy who died when he was left inside a pickup truck tried to save himself from the sweltering heat, detectives told KPRC Local 2.

"The child was aware," said Lt. John Denholm of the Harris County Sheriff's Office. "He was trying to get out, trying to survive."

Cameron Thomas Boone, 3, fought for his life inside a sweltering pickup truck in the parking lot of North Cypress Medical Center on Thursday.

Investigators said Boone got out of his car seat, found an extra key and tried to put it in the ignition.

"It's like he was trying to put a window down or open a door but was unable to," said Denholm.

Detectives said Cameron's mother was supposed to drop off her son at day care around 6 a.m., before heading to work at the hospital, but forgot.

"She just has to be distraught right now," said a hospital employee who did not want to be named.

Fellow employees said Boone's mother works as an operating room technician. They were shocked the incident happened just outside a hospital.

"How could somebody do that? How could you forget your son inside a truck?" said one employee.

Detectives said the mother arrived at work at 6:30 a.m. and did not realize her son was in the truck until her shift was over at 3:30 p.m.

"Her clicker wouldn't work," said Denholm. "She goes to check, why not; there's her son."

He was in the front seat, where he apparently tried to get out. When the mother found him and could not get in, she smashed the back window and rushed him into the emergency room, but it was too late. Detectives said he likely died several hours earlier.

Detectives said temperatures can reach 150 degrees inside a vehicle in less than 30 minutes.

The Harris County District Attorney's Office will determine if Boone's mother will face any charges.

Three other children have died in the Houston area after being left alone in vehicles this year. Another child died on Wednesday after a relative left him strapped in a car seat inside her car for more than 10 hours.