I used to kick rookie's rear ends for not looking up on building searches... hence how I know. 
Best advice you can give yourself. Establish a redoubt in the house where the family gathers, be able to defend it, and have a way out if the situation calls for an exit.
Our place is also the master bedroom... large walk in closet and door to the outside both in the same room. And there is a crawlspace trap in the back of the closet to get us out a different way if need be.

My thinking is I won't try to clear the house, but only cover my wife while she retrieves the kids and secures them in our master bedroom. I'd then join her, secure the door and wait for the police.
Our place is also the master bedroom... large walk in closet and door to the outside both in the same room. And there is a crawlspace trap in the back of the closet to get us out a different way if need be.

-- Rifle, Pistol, Shotgun

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