Existing literature on collective action suggests that social protest activity is often driven by structural out-group grievances. This article explores how a framework of grievance-based social movement participation applies to the digital media realm and how social media are reshaping the protest landscape. Our research looks specifically at the case of the #Ferguson Twitter storm that occurred in November 2014. During a 3-week period, over 6 million tweets were sent with the indicator #Ferguson. We examine the statistics and content of those tweets to show that the Ferguson Twitter storm was driven to an enormous volume by four key mobilizers. Tweet content included structural out-group grievances that reflect established expectations about drivers of social movements and protests. In contrast to the emphasis on violence by traditional mass media, online social movement participants emphasized peace, especially after the conflict escalated and rioting in the streets began.