train and arm with guns, all teachers,supervisors who oversee people and children when gathered in large numbers.

When more teachers, supervisors, managers (not just in schools, but in all heavily populated public places (malls, churchs, schools etc. etc.) are trained and armed, then the people who are considering doing these horrible killings in public places will consider not following through because of the obvious protection that would be known and prevalent. The design of guns is to protect not kill unless absolutely necessary.