Hundreds of teens -- and by some estimates more than a thousand -- packed South Street late Saturday night. It was another flash mob scene and for the first time recently, Philly police were able to contain the crowd. It was chaotic, brought traffic to a standstill and fear of what could happen caused some shop owners to shut down early. No property damage and no injuries reported. Police got the heads up this time from parents who called in saying they'd seen text messages about the flash mob on their kids' cell phones. Three teens were arrested.