Its things like this that I ALWAYS carry. I live in WI so prior to our recently enacted CCW law I couldn't carry outside my personal property. About 11 years ago I lived in an apartment with my now ex-wife and she was always complaining about how I kept a gun on me when we were at home. I told her I'd keep a gun on me when we're away from home too if I weren't breaking the law.
Anyway that year my next door neighbor (literally the next door down the hall) was the subject of a home invasion similar to this - they knocked on his door and the pushed their way in. He was stuck on the head with a flap jack, hog tied and left bleeding in a corner of his living room while they looted his apartment. I heard the noise and commotion and went to investigate. I opened my door to find three men with bandannas on their faces carrying a TV and some other electronics out of my neighbor's place. With my right hand on my 1911 carried at 3 o'clock in an OWB holster I asked them what they were doing. They all turned to look at me, saw I was armed and dropped their cargo and ran.
I went into my neighbor's place to find him tied up so I cut him loose and dialed 911. Luckily for him he only lost some electronics. The crooks hadn't made it to his bedroom yet where he kept a loaded Kel-tec 9mm in his night stand.
If he were armed he might have been able to avoid being struck, bound and robbed.
I'm always armed and I make sure I know who I'm opening the door to. Same goes with my wife.
This is who we are, what we do.