This working paper presents the first results of an exploratory study, funded by the Defense and Security Area of the Paris Police Prefecture. Following a mixed methodology in social sciences, it aims at describing and understanding the ways information appears and circulates through social media at the time of major crisis. Indeed, in France since the 13th November 2015 terrorist attacks in Paris, social media have been occupying a specific position for citizens when it comes to being informed, specifically during such events. We have restricted our observations to Wikipedia and Twitter, as well as two types of events.