Hindsight is like regular sight, only more fingerpointy.

We don't know any details yet, so we are all speculating, which is wonderful. We can fill in the gaps of what we don't know with speculation and come out with a scenario that has little to do with the reality of the shooting. Something bad happened, we're upset, its time to overreact and start demanding blood and blaming things because, I'm so angry I just have to hit something.

I'll add my own bit of thinking in this whole larger issue since everyone else is. As been said, try to state your description and all information you can to the dispatcher, if possible try to stay on the line. Communication is perhaps the best method to keep mistakes from happening. Communications may break down from you to dispatcher to officer, but good intel keeps the best possible chances of avoidance of friendly fire from ever happening. Calling the police and giving them rough information and no updates means the officers walk in blind into a dangerous situation.

Another good reason to stay in your room or where you are at and perhaps not go house clearing by yourself. If you can call the police from your bedroom and stay in there, or saferoom, staying in place and letting the police know your location is another way of keeping confusion down. You go running around your house looking for the intruder you may run into him, or have one of his buddies wander into your back while you are trying to go forward. Or, you wander into the police officer in the dark and have an incident. Although this case seems to have elements which support the home owner, the fact that an adolescent was being assaulted probably meant the homeowner had to move to defend someone, perhaps negating this idea in this particular situation.

On a last note, almost off topic, or at least leading to, the advantage of uniforms, ID's, markers, ect. One thing we can learn from the olden days, where modern people mock the old school for wearing flashy uniforms to musket fights, there was great wisdom. In combat, colorful, identifiable uniforms help to distinguish who is who in the clutter of battle, with all that smoke. Police who wear uniforms today have the advantage of being recognizable in public or elsewhere, you can see who they are, a good thing. Police who wear street clothes run the risk of "blending in" perhaps too well, like the plainclothes officer who was killed by mistake. The all vaunted 'grey man" blends in when he wants, but unfortunately does so when he doesn't.

Contacting police with details is important if possible, whatever contrasts you against the attacker, whatever makes you stand out is a huge advantage. "I'm a guy and there's a dood in my house" isn't good enough when you can try to do whatever you can to differentiate and identify yourself. Wearing a chicken suit may not become part of your self defense strategy, but remember that anything that makes you easy to identify can be a literal lifesaver.