what are the chances of a meteorite hitting a building?

Astronomical but a doctor in Lorton, VA had a close call with a meteorite on Monday. He was doing paperwork later in the afternoon and heard a loud boom. Upon investigating, he found three pieces of what he thought was a rock. Turns out it was a meteorite and probably was traveling at 220 mph when it hit the building. http://www.washingtonpost.com/wp-dyn/content/article/2010/01/20/AR2010012004767.html?g=0