After noticing the children were missing, Randolph told officers she found them unresponsive in a locked vehicle and broke a window to rescue them.
Cynthia Marie Randolph, 24, was busted Friday and charged with two first-degree felony counts of causing injury to a child, NBC Dallas Fort Worth News reported.
In Randolph's initial statements, the sheriff's office told NBC 5, she said the two children had been playing and when she couldn't find them in the house, she started searching the property, eventually locating them in the auto.
Randolph woke to find her two children unresponsive.
After extensive interviews with police, investigators determined that Randolph actually intentionally left the children in the vehicle to teach young Juliet a lesson.
According to documents from the Parker County Sheriff's Department, the mum initially told the police that she had made an attempt to save her children.
In "that version", she said she searched the property for some time before finding the children locked inside a four-door auto, which they'd presumably entered of their own accord and becoming 'locked from the inside'.
Two young siblings died after their mother allegedly left them in a hot auto for three hours as punishment.
In 2016, Romper reported that a child dies from heat stroke after being left in a #hot auto once every nine days on average. According to the data, an average of 37 children die in hot cars annually in the United States. The children were unresponsive and Randolph said she broke a window to gain entry.
Ms Randolph initially said they were exposed to extreme temperatures inside the auto for no longer than an hour.
The children were pronounced dead about a half-hour after authorities were notified, police said.
Bond has not been set for Randolph, who is being held at Park County Jail.
Sheriff Larry Fowler said in May that any incidents involving any child are hard, but this call was "especially heartbreaking" with the unfortunate deaths of the two children, CBS DFW reports.