American teachers will be provided with a simulation to help them protect children in the event of a gunman entering a school.  Since 2000, nearly one-third of mass shootings involved a school according to the FBI. This simulation has been created by Homeland Security and the US Army to help save lives.  It allows users to see through the eyes of a teacher, pupil, police officer or gunman.  This technology has previously been used to prepare soldiers for a war situation.  The simulation can analyse what factors effect outcomes such as automatic closing doors.  Report by Adam Page.