‘I am proud of all of you who have lifted up my voice, my courage and my free spirit,’ echo the imagined words of murdered student Alexander Mora Venancio before a crowd of tens of thousands in Mexico City. ‘I invite you to redouble the struggle, that my death be not in vain,’ continues the letter, written by his father when he learned that recently discovered human remains belonged to his son.

Alexander was one of 43 students from the Ayotzinapa teachers’ college in Guerrero, who were violently abducted by municipal police in September 2014 and turned over to a drug cartel. The cartel supposedly killed them at a garbage dump, burning their bodies and dumping the ashes in a nearby river. An Austrian forensic lab identified the first student from the remains: Alexander Mora Venancio.