¿Quién Mató a Mariano Ferreyra?

¿Quién Mató a Mariano Ferreyra? (Who killed Mariano Ferreyra?) is a documentary work by Martín Caparrós about the murder of Mariano Ferreyra, an activist killed in Barracas, while a manifestation was being held by PO (Partido Obrero or Workers Party), around which several suspicions are being considered, involving Carlos Tomada, Argentina's capitol city Minister of Work and Social Security and José Pedraza, a railway syndicalist.