Let Him In?

Was the Texas shooter allowed into the school? Was the building secured with locked doors during the course of the day, except during drop-off and pick-up? If not, why was an entrance open to a potential murderer? There apparently was a school resource officer. Was that guard armed? Did he (or she) engage the perpetrator of the massacre? Law enforcement that is there or arrives during the course of mass shootings does no good if it sits out the fight waiting for tactical officers to arrive. An officer with a pistol stands a much better chance of survival against a gunman than a bunch of unarmed ten year olds. Who knows, with enough courage and luck, that overmatched cop might just take out a potential killer and save innocent lives.