This paper offers a comprehensive approach towards analyzing and explaining the role of Twitter in shaping and facilitating social movements especially during protests. It presents automatic and manual analyses of the tweet themes, usage characteristics and major Twitter users during a public outcry against a gang rape incident in Delhi, the capital city of India. Our results identified Twitter as an important channel of diffusion of ideas with the ability to share news and ideas rapidly among a vast set of adopters defying geographical boundaries. Results of the content analyses highlight the prominent use of social media resources in disseminating information on Twitter, and the remarkable role of Twitter users as citizen journalists during the days of the protest. Results of the social network analysis suggest that major role players on Twitter were the offline protest leaders.