A schoolgirl in Pennsylvania has been held by Police after plotting a mass shooting at Radnor High School. Courtesy FOX 29

POLICE in Pennsylvania believe they may have foiled another high school shooting after teachers discovered the disturbed writings of a 17-year-old female student.

The girl, who attended Radnor High School, northwest of Philadelphia, had developed an obsession on the Columbine High School massacre of 1999 and wrote to the parents of one of the perpetrators.

“I could be the first female shooter,” the girl had written in one of her school notebooks, which was discovered by a teacher.

The girl was arrested on Monday and is receiving care. Police said she had a history of psychological issues.

The Mirror quoted Police Superintendent William Colarulo, who said: “She made references to killing a teacher, killing fellow students in a certain manner, and also injuring herself.”

“I want to trap them, pick them off one by one,” she is alleged to have written in her notebook. “Blow up the cafeteria, shoot everyone in classrooms. Imagine the power, the bullets leaving the gun with a loud bang, piercing kids around me, the way they collapse, their blood splattering the floor, the screams.”

The two notebooks contained other disturbing passages, such as “flood the halls with corpses” and “I’m about to get very violent”.

Colarulo said the police would be “remiss” if they had not taken the threat seriously.

“As soon as it was recognised that these writings were bizarre and dangerous the appropriate steps were taken,” he said. “That’s what we hope people will do from now on.”

The mother of a student who spoke to NBC, Debbie Singer, said it was a relief that the girl did not have access to a gun at her family home.