How much blood money needs to be paid (and by who) if a person is killed by a stone falling from a building's surface covered by stone?

We are living in a 5 floor building near a main street in city. The building's surface is covered by stone (Travertine) and is in dominant position on the sidewalk. The question is: How much does it cost and who has to pay the blood money if one piece of the stones for no reason fall on one's head and cause him to die?