They probably thought these drills and plans are a lot of trouble and a waste of time; something like that will never happen in our little town.
My daughter is in her final year of nursing school and experienced a real active shooter threat at the hospital where she works.
She said all the nurses panicked and blanked out. It took them several minutes to get their shyte together and remember what to do. Fortunately she was floors above the threat (fired employee) and hospital unit doors are always locked and the lockdown deactivates the id card readers that open them and the elevators also. Some wings also have double sets of doors (man trap) like OB and NICU to prevent infant theft.
So all they really do is direct ambulatory patients to hide in their bathrooms while the nurses pull all the privacy curtains and close the room doors and then go lock themselves in the janitors closet.