From the preview:
Almost every member of the Cult of the Burning Man began their twisted worship as one of the Broken. People who had experienced significant trauma in their lives were particularly receptive to the call of the Burning Man, and their first act is often one of intense violence against their loved ones. The Broken tend to gather in large groups, rambling their madness to one another and gathering up whatever impromptu weapons they can find. Over time, chaos and violence thin out their numbers, some progressing deeper into the Cult while others are killed. Fortunately, there is never any shortage of madmen to replenish their ranks.