Agreed. I work in a school and I am ALICE trained. It is possible they did run toward the sounds of gunshots which is what made him barricade himself in a single classroom when his initial plan was to go room to room.

Once he is in a a single classroom with the door locked/barricaded/unopenable they have to change plans, because they can no longer individually access the shooter. School doors are usually heavy wood/steel that open outward on steel frames embedded into concrete (specifically to stop school shooters from entering.) Despite what a bunch of keyboard Hulks claim, there is no way they are kicking the door in.

No one on reddit knows what happened, or what took them so long to access the room, and trying to blame everything on the cops when no one knows where the failures occurred potentially takes the conversation away from the school (why were doors not locked), from larger political issues (like gun control, mental health, or toxic social cultures), or even the police! If there is a failure of training or tactics, you can't criticize that if everyone is just rolling around on the ground in hysterics about "coward police."