When probed on how long the children were trapped in the sweltering vehicle, their mother, 24-year-old Cynthia Marie Randolph said, "no more than an hour" and that the kids had somehow locked themselves in the auto on their own.
Cynthia Marie Randolph, 24, was being held Saturday on 2 counts of triggering severe physical injury to a child.
The incident happened at Ms Randolph's home near Lake Weatherford, the Parker County Sheriff's office says.
It says that when she woke up and went to check on the children, they were unresponsive and she broke the auto window to support her initial story.
Over several interrogations, police were able to see through Randolph's changing story.
Randolph proceeded to go inside the house where she smoked marijuana then fell asleep for two or three hours.
Temperatures reached approximately 96 degrees that day.
She said that day she found the children playing inside the auto and told her daughter to get out. She later told authorities she had found the children playing in the vehicle and began screaming at the daughter, demanding her to get out. CBS Local stated that Randolph implicated herself in the deaths of her children during an interview with Texas Rangers and the U.S. Department of Justice Inspector General.
Authorities were called to the home at about 4 p.m. when the mother said she had discovered them unresponsive in the vehicle. She claimed that she broke one of the car's windows to try to save them.
Both kids were pronounced dead at about 4:30 p.m., according to FOX4.
While many parents have accidentally left their children in hot cars that have resulted in their deaths, this case may prove to be problematic for prosecutors.
No bond has been set yet for Randolph, and it is not clear whether she has an attorney.