I see. Well, how about this? "I just wanted to tell you smoke and flames are pouring out of your attic. I called the fire department but wanted to alert anyone in the house." So was there a fire at the homeowners house that our "good citizen" felt compelled to tell him about?
How about, "Your son was injured down the street, Mr. Smith, and I thought you'd want to know immediately."
Was our "good samaritan" trying to inform the homeowner that his son had been injured?
Or was the "angel child" knocking on the door as a prelude to a violent home invasion or robbery?
I guess you missed the point I was making by my hypothetical examples. There are perfectly good reasons why people would knock on your door late at night and very good reasons why you would appreciate that they did. An adult with a loaded firearm is expected by most people to be responsible enough to make an effort to determine the nature of the knock before summarily blasting away.