Of course I am a lunatic, yet the gun fire was from outside of the building. Maybe there should be a law to make building walls strong enough to keep gunfire from penetrating and killing a person in another building.
According to media reports, such as the article shown in the video linked at post 32, the building has a brick exterior. They might be just a thin decorative veneer, or maybe the bullet passed through a window or other surface, but if a brick won't stop the round you are in a situation where your building should probably be a bunker.