“The accident took place in a pair of four-story buildings at 22nd and Market Streets that were reported to be under demolition at the time.”
http://philadelphia.cbslocal.com/2013/06/05/building-collapse-in-center-city/
hey here’s live video
http://www.nbcphiladelphia.com/news/local/Building-Collapse-in-Center-City-210243621.html