Authorities say a teenager was traveling at more than 100 mph while high on opiates when she crashed her car into a house in Frankfort, Indiana, last month — killing an 8-year-old girl and her 17-year-old sister inside, PEOPLE confirms.
On Friday, 17-year-old Alia Sierra appeared in an Indiana court where she learned she had been charged as an adult with 10 criminal counts, including reckless homicide, causing death while operating a motor vehicle with a controlled substance in the blood and criminal recklessness.
Sierra pleaded not guilty to the charges. PEOPLE was unable to reach her attorney for comment. She remains in jail pending her trial, which is scheduled for November.
The July 12 wreck killed Callie Fullerton and her older sister, Haleigh Fullerton. Authorities say the sisters were snuggling on a couch, watching TV, when Sierra’s 2007 Honda Accord slammed into their home, pinning them both beneath it.
Their mother was also injured in the crash but is expected to make a full recovery.
Soon after police arrived on the scene, Sierra allegedly told investigators, “I killed those kids, man,” according to an affidavit obtained by PEOPLE.
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Police said Sierra was driving with four passengers at the time of the crash and estimate her speed was 107 mph.
One of the passengers told investigators that she had asked Sierra to slow down. The affidavit states that another passenger said Sierra allegedly told them her car was “the beast” and that she talked about how fast it could go.
Sierra told police she was driving 80 mph when she hit a bump and lost control of the car.
After the wreck, her urine tested positive for opiates, authorities said.
A GoFundMe has since been set up to support the family of the slain sisters. It reads, in part, “These two beautiful ladies were taken too soon and while their time on this earth was short they touched every hear they came in contact with.”