We had a hostage situation at a university where I worked. Assume there had been a warning system in the building. What should the proper response have been? For example, should one try to evacuate or barracade themselves. The answer to that question requires informed insight, not suppositions. Children locked in a classroom might be far safer than in the hallway trying to get to an exit. So, part of the plan may be to ensure that interior doors have locks, windows open (?), two-doors in every room with students, etc.