Updated

A 14-year-old Pennsylvania teen was accused of stabbing her older sister to death inside their home while their parents slept early Monday, officials said.

Claire Miller, of Manheim Township, was being charged with criminal homicide as an adult in the death of her 19-year-old sister Helen, the Lancaster County District Attorney's Office said.

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"This certainly is an incredibly tragic and unusual case," District Attorney Heather Adams wrote in an email to local station FOX43.

Officers responded to the home just after 1 a.m. Monday after the teen called to report that "she had killed her sister," the district attorney's office said.

Miller was arrested at the scene and was being held without bail at Lancaster County Prison, the district attorney's office said. (Photo: Lancaster County District Attorney) (Lancaster County District Attorney)

Court documents obtained by local news outlets described her as "hysterical" while on the phone.

When officers arrived at the home, they found Claire Miller standing outside and spotted what appeared to be blood in the snow near the driveway, according to a police complaint obtained by Lancaster Online. The teen also appeared to have blood on her pants.

Officers said they heard her repeatedly say, "I stabbed my sister," and watched as she appeared to try washing her hands in the snow.

Claire Miller pointed the officers to a bedroom where they discovered 19-year-old Helen Miller with a stab wound in her neck, officials said.

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Helen was found lying on her back with her hands up near her head and a blood-stained pillow covering her face, according to the complaint. The "large knife" was still in Helen’s neck, just above her chest, when the officers removed the pillow.

First responders attempted life-saving measures but were unsuccessful, officials said.

Investigators determined that Helen had been stabbed sometime overnight while the girls' parents were sleeping. No further details on what led to the incident were immediately available.

"I don't know that I have ever been a part of something that is quite as sad as this," Manheim Township Police Chief Tom Rudzinski told WHTM-TV.

Claire Miller was taken into custody at the scene and was being held without bail at the Lancaster County Prison. She was charged as an adult because homicide is not considered a delinquent act in Pennsylvania.

The tragic news shocked the community of Manheim Township, which has a population of about 38,000.

"It's not the kind of thing we would expect in our neighborhood," Sarah Delia, a neighbor who said she did not know the family personally, told FOX43. "It's very quiet and peaceful."

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Steve Lisk, head of school at Lancaster Country Day School where Claire Miller was enrolled as a ninth-grade student, told the station that the "tight-knit school community" was "surprised" and "grieving" over the news. The school was offering counseling services.

A preliminary court hearing for Claire Miller was set for Feb. 26.