Ideally it wouldn't get this far but at a minimum, the police should not shoot until an actual gun is seen. Thinking they are in danger is not good enough, their rules for engagement need to be as high as the military, if not higher... they should have to confirm there is an actual threat and should not fire their weapons until at least that threat is confirmed. A feeling is not enough to shoot on.
I don't think it's the training standard, but it is the most common defense in court. Somehow military soldiers are able to resist these feelings and have much more strict rules of engagement. Citizens should have the same protection against being shot at by the police that terrorists get from being shot at by the military. I don't think that's too much to ask.
