The security wasn’t good at the school and the police should have acted quicker, but what if the killer shot the parents when they went in?
Freedom isn’t free.
It takes a bit of training and guts to attack a site defended by criminals, enemy combatants etc. Training soldiers to advance forward under fire is done every day and the results witnessed by actions of young men in every war we have had. There will always be those that freeze or refuse to advance. Those have to live with the placard of 'coward' around their necks forever. For the sake of a few missing in action brave souls in that school, some if not all the children would be alive today.