A staff member discovered the message "I have a gun" handwritten lightly in pencil on a ceramic wall in the boys bathroom. Police and the school resource officer were immediately notified at 10:45 a.m.
Officials said the knife was unrelated to the note found in the bathroom.
Superintendent Cynthia Zurchin said the student had been involved in an earlier altercation with another student outside of the school district and had the knife. He was immediately taken into custody and has been sent to a detention center, she said.
Police departments and K-9 units from surrounding communities and counties quickly responded to the school, which was placed on lock down meaning no one could enter or leave the school building.
Authorities swept room to room, searching backpacks, lockers and purses. The investigation took less than two hours before classes resumed.
"I can tell you, I was very very pleased and proud of the students and staff here at the high school. They remained calm and cooperated fully with everything that was going on," she said.
Messages were sent out to parents and the community informing them of what went on.
Zurchin said the principals met with staff after school to review what went on. On Thursday, she plans to meet with top administrators to talk about all of the safety procedures and operations in the district.
"It is unfortunate in the society that we live in that we must practice for these things and that our students have to be prepared and have to sometimes deal with this situation."
Assisting departments included Harmony Township, Economy, Aliquippa, Beaver Falls, Ohio Township, Ellwood City, New Castle, Mahoning Township, and Neshannock Township.
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