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Relatives of 43 missing students from the Isidro Burgos Rural Normal School of Ayotzinapa hold up their fists behind photos of their missing family members at a press conference in Mexico City, Thursday, Sept. 15, 2016. The former head of investigations for the Mexican Attorney General’s Office, Tomas Zeron, who has been criticized for his handling of the case of the disappeared students, was named a national security adviser hours after he resigned his previous post. The students were in Iguala on Sept. 26, 2014 to hijack buses to use for transportation to a rally in Mexico City when they were attacked on the buses by local police and allegedly handed over to members of the Guerreros Unidos cartel. (AP Photo/Marco Ugarte)