MANHEIM TOWNSHIP, Pa. (WHTM) — A 14-year-old Lancaster County girl is charged with killing her wheelchair-bound sister.

Police said 14-year-old Claire Miller stabbed her 19-year-old sister, Helen, to death inside a home on Clayton Road in Manheim Township.

Court records show that the 14-year-old called 9-1-1 a little after 1 a.m. on Monday hysterical, saying she “she killed her sister.”

“When I heard about this I was almost instantly upset about it myself over the details that had been related to me,” Manheim Township Police Chief, Tom Rudzinski, said.

Court records also show that when police got the home Claire Miller directed them to a bedroom where Claire’s older sister, Helen who had cerebral palsy, was found lying on her back with a blood-stained pillow on her face.

The same court documents show that once police removed the pillow they found a knife in Helen’s neck.

“I don’t know that I have ever been a part of something that is quite as sad as this,” Rudzinski said.

Rudzinski told ABC 27 News that the murder happened while the girl’s parents were asleep, and also inside the house.

Claire Miller, photo courtesy of Manheim Township Police Department

Police are still working on determining a motive for the killing.

“The investigators are going to be asking those types of questions, conducting those interviews of everybody that was involved, and trying to determine a timeline exactly what that would have lead to this awful event,” Rudzinski said.

Claire Miller is being charged as an adult.

Lancaster Country Day officials confirm that Miller is enrolled as a 9th grader at the private school.

Miller is in the Lancaster County Prison, and is being held without bail.