Beats me. Took shelter management courses in the Air Force and never heard of it. Some Clymer made it up during the search for the Boston Marathon bomber. I wonder how long the shelter in place course is for soldiers.
“shelter in place” means: hide in your building, hope that no one comes in and kills you, while you are only permitted to stand there and not fight back.
It is unclear if praying to God is currently permitted or not (this last sentence is sarcasm)