What is known for certain is that teenagers—summoned via social networking—met on South Street on March 20 - and in Center City on March 3, Feb. 16, and Dec. 18. In each of the four incidents, which some are calling “flash mobs,” violence broke out. The teenagers involved were overwhelmingly African American males, although prosecutors say a significant number were girls. It's wise to keep in mind that the everyday violence and abuse that many poor teenagers live with "depress them and keep them stressed," said Phil Harris, a criminal justice professor at Temple University. Quick fixes won't come easily.