Arriving five minutes later, officers were waived down in the front driveway by the teen, who repeatedly said "I stabbed my sister". There was blood all over her pants, and in the snow in the yard.
"Miller appeared to be attempting to wash her hands in the snow," police observed.
Entering the home, they found Helen, a wheelchair-user, lying in bed with a blood-stained pillow covering her face. Pulling back the pillow, officers saw a large knife still embedded in her neck, just above her chest. She was lying on her back with her arms above her head, blood pooling around her.
"Lifesaving measures were attempted; however, were unsuccessful," the complaint states.
Police said the parents were at home at the time of the attack, but were asleep.
"Looking for evidence and trying to come up with a timetable and whatever they can find to help them understand what might have happened," Manheim Township Police Chief Tom Rudzinski said.
The motive remains unknown.
The teenager was arraigned on a homicide charge, and is being held without bailat Lancaster County Prison. She is being charged as an adult.
"Anyone charged with homicide in Pennsylvania is not eligible for bail," Lancaster County DA's office said in a statement the following morning. "Claire Miller is being charged as an adult because homicide is not considered a delinquent act in Pennsylvania."