The Monroe County Sheriff's Office said a 3-year-old boy is dead after he was found inside a locked car.

Deputies responded after the child was found unresponsive in a locked car after being left there for around 35 minutes.

Monroe County deputies said they arrived on the scene at 1:15 p.m. Monday. Attempts to revive the child were unsuccessful.

The death was a result of the heat, and the investigation is ongoing.

Investigators said they spoke to the child's grandmother and guardian, who said she had been mowing the neighbor's lawn at the time.

The grandmother told authorities the child had been left in the care of a 15-year-old at the residence who was watching other children at the time.

At some point, the grandmother noticed the boy wasn't around and asked the teen where he was, according to deputies.

When they eventually located the child in the car, the grandmother said she took him inside and tried to revive him, but was unsuccessful.

Deputies said the vehicle's doors were locked and unable to be opened from the inside with the handles.

The grandmother said the car had been parked at the residence that morning and had not been moved. An incident report states it wasn't clear if the vehicle was locked when it was parked.

The child was taken to Sweetwater Hospital.

Monroe County Sheriff's Office spokesman Lowell Russell says these types of calls are some of the hardest for first responders.

"Calls like this really tug at your heart," Russell said.

First responders are often faced with the unthinkable.

"You always carry calls like this not only through your career, but through your whole life," Russell said.

Monroe County Sheriff's Office spokesman Lowell Russell says calls involving children are the toughest.

"We just need to keep the family and the first responders in our prayers and thoughts," Russell said.

The medical examiner plans to perform an autopsy Wednesday.

Russell says those results will help determine if there are charges in the case.

"All you can do is listen, and try to do the best you can," Russell said.

He says preventing these types of situations is top priority for the sheriff's office.

"Part of that is to teach our children the dangers of hot vehicles, and other things around the house like swimming pools or electrical outlets," Russell said.

First responders say if your kids do somehow get stuck in a hot car, it's important they know to reach over and unlock the car, or honk the horn, even at a young age.

"Something else we try to do is make sure they lock the doors so the kids can't get in there, but we also try to make sure that they hide their keys or key fobs so the children can't get those and sneak inside the cars without the parents knowing," Russell said.

Russell says parents should use this latest tragedy as a reminder.

"People see it on TV and they think it can't happen to me, and they find out, unfortunately, it can," Russell said.