(KRON) — A student at Palo Alto High School was taken into custody for writing that they intended to “shoot up” the school during finals week, the Palo Alto Police Department said in a press release. The incident happened on Tuesday, causing a shelter-in-place.

Officers were called to the school, located at 50 Embarcadero Road, at around 8:57 a.m. School administrators told dispatchers that a teacher had arrived at school and found a threat of violence taped to the front door of a classroom.

“The threat indicated that the person who left the note intended to ‘shoot up’ the classroom later that morning,” PAPD said.

Police said that a final exam was scheduled to happen that morning in the classroom where the note was posted.

The shelter-in-place was kept in effect until about 10:30 a.m. as a precaution, per police. Over the next two days, school officials and police worked to identify a suspect.

On Thursday afternoon, a 17-year-old male Palo Alto High School student was identified as the suspect. He was arrested for criminal threats, which is a felony, and released to his family members.

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Police said there was no evidence the boy ever had access to a firearm. Due to his age, he was not publicly identified by PAPD.