Welcome to GT.
The case you cite is a tragic one.
"Information to share with a potential attacker" might include the phrase, "We've called 9-1-1! Police are on the way! Leave now!"
We don't seem to have the full story in the newspaper report. Opening the door to an unidentified person exhibiting aberrant behavior is never a good idea. Crazy/messed up family members are a 'wild card' that is often overlooked by people planning for self-defense.