What is the importance of the Disciples in the nonfiction book, Gang Leader For a Day?

The Disciples was a rival gang of the Black Kings. During a dispute over drug territory, two young kids at Robert Taylor were shot by members of the Disciples in a retaliatory drive-by. The little boy survived but the little girl died. Parents with little kids at Robert Taylor were terrified and kept their kids inside. A meeting was arranged between the warring gangs and a truce was agreed to. A little girl had died but that was just the way things were.