Did the school have security people in the school prior to the attack?
If not, then that would mean that anybody could walk into the building before lockdown time.
This kid had to stand out like a sore thumb. Black paramilitary style clothes, too young looking to be a parent. Anybody taking a second look would have known that he was out of place.
It is great to have security protocols in place, but everyone has to take them seriously and respect them. I have a feeling that something went seriously wrong with the SOPs that were supposed to be in place. I hope somebody did not stop by the cafeteria in an attempt to score another donut or something.
I have seen a lot of talk on the web this evening about what if teachers had been packing. It may not have saved many lives, but if everybody knew that every adult in a school building was packing, then there would be far fewer of these episodes.