buenos air family young protester go miss argentina nearly three months ago identify body friday say brother dead man journalists leave morgue investigators discover body tuesday chubut river patagonia near santiago maldonado last see indigenous right protest aug. 1. recognize santiago tattoo convince santiago say sergio maldonado brother family identify body buenos air government opposition right group say state security force take maldonado 28-year-old craftsman police reportedly clash mapuche indians claim territory throughout southern argentina chile group allege president mauricio macri government cover maldonado whereabouts macri government say evidence show security force detain disappearance death maldonado overshadow sunday midterm congressional election country potential case abuse security force particularly sensitive argentina 1976-83 military dictatorship secretly detain torture kill people clandestine prisons right group say 30,000 people disappear judge oversee maldonado case say autopsy complete late friday show sign injury body cause death need determine judge gustavo lleral tell journalists former leftist president cristina fernandez seek senate seat buenos air province criticize government handle case mass protest social media campaign demand know happen maldonado president office say friday macri contact maldonado mother offer condolences mourners leave candle flower card outside morgue buenos air protesters gather plaza de mayo miss argentine protester 's body identify days election