A training exercise at Naval Base Ventura County used a scenario that is all too true to life.  They had a man pretending to be a school shooter hiding near a base military academy.

Organizers in Port Hueneme call it their annual force protection exercise.
Ventura County sheriff's deputies, firefighters and K-9s took part too.
One trainer said you can't just prepare on paper, or you will lose your proficiency.

Those taking part in the training eventually found the shooter hiding in a storage shed.