<p>Young people run down South Street in Philadelphia during a flash mob incident that involved thousands and closed the street to traffic from Front Street to Broad on March 20.</p>
August 14, 2011
Stories this photo appears in:
August 14, 2011 9 p.m.
Could it happen here?
UK violence raises questions about American unrest
A black man killed by police. Mobs of looters. Cities charred and shaken. The riots in London mirror some of the worst uprisings in modern U.S. history.