Abstract--Microblogging sites allow users to post short messages online, offering a reliable way to communicate and to spread information quickly and efficiently; moreover, they can host complex conversational activities. The objectives of this paper are to model how breaking news circulate in a microblogging network, to identify relevant patterns of news propagation and to increase our understanding of the underlying sociological motivations. This study has been conducted on a real social database collected from a well known microblogging site by observing the reactions of its users to a relevant public event.