Criminal minds are interested in possibilities, that is, what can we get away with and for how long? Notice how realistic the “fake” guns are and that the bearers of them were studiously ignored (lest teachers be found guilty of racism, bigotry,xenophobia) until the weapons were openly displayed and actually pointing at children. If the intruders had instead been members of ISIS there would have been another massacre.
They claimed to be from ISIS.
What makes you think they are not.
Or won’t be by tomorrow.