French people were astonished to learn of the death of an opponent to the construction of a dam in the Sivens forest, in the Tarn department (France), during clashes with the police on the night of 25 to 26 October 2014. However, the violence of the means deployed to realize this work and the determination of opponents, together woven in the play of all the actors of this project, foreshadowed the possibility of such a drama. Using a formal analysis framework based on the sociology of organized action, we present a model of this interaction system whose simulation results highlight the overdetermined nature of the emergence of a conflict of extreme intensity. Variations in this model allow the identification of the main determinants of this conflict and to consider other possible futures.