Teachers at the school risked their lives to save their students, including one who was shot (not killed) getting children to safety.
While you may have the "that kind of thing will never happen around here" attitude about it, the reality is that tragedy can happen anywhere. Even though the odds of anything every happening may be low, the possibility is still part of the job. Teachers and administrators would be wise to be prepared for the worst of the worst.
Hopefully nothing terrible will ever happen at your school. If it does, though, be prepared to do what you have to do to protect your students.