CHILPANCINGO, MEXICO - OCTOBER 08:  People protest the disappearance of 43 students from the Isidro Burgos rural teachers college and demand authorities find them in Chilpancingo in southern Mexican state of Guerrero on October 08, 2014 in Chilpancingo, Mexico. Federal agents have been sent to the area after the discovery of a mass grave and charges that local police may have conspired with a criminal gang to kill and disappear the students. (Photo by Miguel Tovar/LatinContent/Getty Images)