After the Columbine shootings the “words of wisdom” was to huddle together, stay in place. My daughters were in high school and I told them not to do that unless they wanted to die. I told them their real choice was to flee or fight and it depended on the situation which would be best. I have no idea who the genius was that thought students should stay in place or huddle together. Sure make great targets that way.
By the way, in the workplace, any shooter is almost guaranteed to be a disgruntled worker -- and he KNOWS where everyone has gone to. Great big crowd of sitting ducks.
The current advice of "just run" is superior.