The accused student is 17 years old. The teacher had previously warned about the danger posed by the student.

Teachers in schools in Istanbul, Turkey, went on strike on Tuesday to protest the killing of a teacher at a high school, in a shocking crime that renewed concerns about the spread of violence in schools.

According to initial reports, a 17-year-old student attacked his teacher, Fatma Nur Çelik, 44 years old, with a knife inside the classroom on Monday in the Çekmeköy area on Istanbul’s Asian side, resulting in her death at the scene.

During the attack, another teacher (52) and an 11th-grade student (15) were also injured as they tried to intervene before police arrived and arrested the assailant.

Turkish media reported that the biology teacher who was killed had previously warned about the danger of the student due to his repeated involvement in fights, his nervous condition, and his prior treatment at a mental health hospital.

The sources added that the student left the hospital with his father only two days before the crime and studied the school timetable to identify the class of the targeted teacher, then planned his attack accordingly.

The Public Prosecutor's Office launched a wide investigation into how the knife was brought into the school and whether anyone assisted the student in planning the crime.

In reaction to the incident, teachers in Istanbul, home to some 16 million residents, stayed away from schools on Tuesday to protest and prevent such violent incidents in the future.

Simultaneously, teachers in other Turkish cities held similar demonstrations, demanding effective security and stricter monitoring in schools to ensure the safety of students and staff.