I wanted to address this particular quote separately. There is no such thing as a foolproof plan, especially involving firearms and high stress situations. We have a saying in the military: no plan survives the first round fired. You have no idea how your kid or wife would react to the alarm going off, much less rounds being fired. In fact, I’m guessing you have no idea how you or your SIL would react, which is troubling because you’re both carrying weapons in your scenario. If I was in your shoes and had the resources you claim to have, my plan would be as follows: son runs to mother’s room and lock/barricade the rooms with people in them. Call the cops. Be prepared to throw on lights so you can see them before they find you in the room - they have to ID themselves by breaking down the door giving you the advantage of concealment and time. When cops arrive, listen to their instructions if the person is still there as they are trained for the scenario you lay out. In all likelihood, bad guy left and your home security system probably recorded them (I’m assuming you have cameras since you seem so security conscious). Going vigilante in your house is a bad plan unless you’ve got some sort of previous training that you haven’t revealed yet.