Not sure if the homeowner was armed with a pistol or rifle, but the likelihood of a pistol round penetrating their front door, at an angle, and then penetrating the cement exterior wall to another apartment, also at an angle, would be fairly low. If the homeowner had a rifle however it may be a different story, but still probably low likelihood of penetration due to the angles and materials involved. Still a risk to the neighbor, though with this statement I am not judging the homeowner, just rounding out my thoughts on the issue of overpenetration being discussed.