Heartbreaking tragedy: Dad 'under pressure at work' leaves twins to die in hot car by mistake

Richland County coroner Naida Rutherford on the death of twins Bryson and Brayden McDaniel. Video / WIS TV

A father has lost his two young children after he accidentally left them in a hot car for the entire day while he was "under pressure at work".

South Carolina authorities have ruled the deaths an accident, after the 20-month twins died from hyperthermia when their body temperatures were extremely elevated, the coroner ruled.

The father thought he had taken his boys to daycare and then drove to work.

But when he finished work at 5.30pm the same day he found his boys in their rear-facing child seats after driving to the daycare to pick them up.

On Tuesday, Richland County Sheriff Leon Lott confirmed no charges would be filed.

Lott said that the man had been dealing with work-related issues and that the deaths were a "horrible, horrible, tragic accident".

"The father was under intense pressure at work that really had his mind somewhere else that day," Lott said.

"He really believed he had dropped the two boys off at daycare.

"There was no doubt in his mind that he had done that."

One of the twins' parents discovered the children in the backseat. Photo / NBC

Police have decided not to name the father, saying speaking with him has been "heart-wrenching".

"There were some things going on at work, not your normal work activities, just some things that were going on that he was dealing with at work. That contributed to it," Lott said.

"The pure emotion that came out was not something that you could fake," he said.

"This family needs prayer, their life will never be the same."

"Nothing's going to replace these two boys.

"Nothing's going to take away the pain this family is going to feel."

Rutherford said the tragic events should serve as a tragic reminder for parents to check the backseat before going to work.

"We hope that this is an example for parents to just pay attention when they get out of the car to make sure that they actually drop off their children."