48 Hours - 17x13 - Without Warning, Chaos- Followmy.tv

It was the first really warm summer night in Chicago's Lincoln Park, and a group of kids, most just out of college, were looking to make the most of it. The bars and restaurants were packed, and if you weren't out on the town, then you were likely to be partying out on the back porch of one of thousands of old row homes or apartment buildings in the area. On June 29, 2003, there was only one party to be at – a two-story bash thrown by a group of young professionals who lived there. "It was a good atmosphere," recalls pediatric nurse Katie Main. "There was a really great group of people." But in less than 10 seconds, the carefree party would turn into chaos -- and 13 people wouldn't get out alive. Correspondent Maureen Maher reports.