Tobias Hansson, the principal of Grimstaskolan in Stockholm, Sweden shares critical learnings from a knife attack that occurred at the school in May 2023. This interview is a vital case study in school safety and crisis management. Summary: The incident occurred shortly after lunch when an outsider entered the school and acted threateningly. The school’s response involved quickly understanding the severity and sheltering (invacuation and lockdown) all students inside the building for safety. The situation was quickly assessed. The decision to shelter/invacuation, opposite to evacuation, was communicated to all employees by raising the alarm in Cosafe. Staff had trained for such scenarios, including active shooter drills led by the education administration in Stockholm (all public schools in Stockholm use Cosafe). The training involved facing different incidents and how to act in emergencies, including ongoing deadly violence, invacuation, lockdown and barricading in classrooms. Students were deliberately not involved in the training