As more information comes out it's sounding more and more like the cops fucked this one badly.
They were more interested in keeping parents away from the school, even to the point of pulling tasers on them, than doing the recognized right thing which is to go in hard and go in fast.
They sat back while he slaughtered the kids.
I think the idea that you shouldn't be able to defend yourself but instead wait for the police to come and save you can be torn up and burned. It's done.
Some of it is likely them wanting to protect themselves, but another aspect is that the last few years must have surely make the police afraid to act and pull a trigger. It could end their life if they make a mistake.
We need to go back to people having a personal responsibility for their own well being which involved not being a dick by doing something that could get you shot.
Everyone of the witch-hunts for police contributes to change. It affects how many police are experiences and how quickly they are likely to act. Not all change is good.