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Two people are dead and at least four others were rushed to a hospital after a gunman opened fire at a public library in New Mexico, Aug. 28, 2017. Getty Images

19-year-old Amanda Hawkins, a mother of two, was arrested in San Antonio, Texas, on Thursday and faces two counts of child endangerment, according to the Kerr County Sheriff's Office. Authorities said Friday Amanda's toddlers died Thursday after their mother intentionally left them in a hot car for more than 15 hours.

Amanda's bond has been set at $35,000 for each count she has been charged with, officers said. Hawkins is now being held at the Bexar County Adult Detention Center in San Antonio, and is expected to be transferred to Kerr County, the sheriff's office said.

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“This is by far the most horrific case of child endangerment that I have seen in the 37 years I have been in law enforcement,” Kerr County Sheriff Rusty Hierholzer said in a news release Friday.

On Thursday, Hawkins and her unidentified 16-year-old male friend took the children to Peterson Regional Medical Center in Kerrville. However, the toddlers were found to be in “grave condition” and were immediately transferred to the University Hospital in San Antonio, a news release from the Sheriff’s office said. Hawkins told the doctors her children had been smelling flowers and thus might have come in contact with some poisonous object.

On Friday, the Sheriff’s office said Hawkins’ was lying and she had left the girls in her car for over 15 hours while she was at a friend’s place.

Brynn Hawkins, 1, and Addyson Overgard-Eddy, 2, were declared dead at the University Hospital in San Antonio around 5 p.m. EDT Thursday, the news release said.

Officials became suspicious of the 19-year-old mother when she told the doctors that her children were at a nearby lake smelling flowers before they collapsed.

“They thought maybe they'd gotten into something poisonous, that's what their story was,” Hierholzer told Fox 29 in San Antonio.

Investigators said that the mother left her children in the car on Tuesday night, while she was visiting a friend’s house and did not return to them until about noon on Wednesday. Temperatures went as high as the 90s on Wednesday morning, Hierholzer told Fox 29 in San Antonio. The sheriff however has not mentioned the exact cause of the deaths.

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“She left them in the car, intentionally in the car, while her and the 16-year-old male friend were in the house,” the sheriff said. “They were in the house all night. The male friend for a little bit went to sleep in the car a little while but then went back to the house.”

The sheriff also said that people inside the house reported hearing the children crying, however, nobody went to check on them.

When Hawkins took them out of the car on Wednesday afternoon, they were already unconscious. She “did not want to get into trouble” so she tried to bathe them and did not take them to the hospital immediately, the sheriff said.

In an interview with the San Antonio Express-News, Alisha Eddy, who the publication identified as Hawkins’ mother, said, “I don’t agree with what happened,” but added, “I love my daughter. I’m there for my daughter.”

The sheriff stated that the charges against Hawkins can likely be upgraded after the case is placed before a grand jury. The 16-year-old male, who was there along with Hawkins might also face charges.