The first clue that Mengele was dead and buried in a remote Brazilian cemetery came from Paraguay. A letter suggested that a man named Hans Sedlmeier, formerly deputy manager of a Bavarian factory owned by the Mengele family, might have assisted Mengele in Brazil. Sedlmeier was a familiar name to the Nazi hunters.
By the 1960s they suspected he was in contact with Mengele, believed to be hiding in South America. West German police raided Sedlmeier's residence, finding correspondence with an Austrian couple living in Brazil, the Bossarts.West German authorities then turned to Brazil, which raided the couple's home. The Bossarts admitted that Mengele had been present at the house, and that he confessed his identity after living there for a year or two. They added that they hosted him for many years, and "he was always afraid that the Jews would come and get him".
The Bossarts said they had gone on vacation with Mengele in February 1979, one afternoon he went for a swim. While in the ocean he suffered a massive stroke and began to drown. By the time he was dragged to shore, he was dead. People didn't find out about Mengele's death until the mid 1980's when Nazi hunters, using newly discovered information, uncovered his grave marked "Wolfgang Gerhard" at Embu.
One of the most important factors in identifying the body exhumed by Brazilian police, was the fact that Mengele had fractured his pelvis in a motorcycle accident at Auschwitz in 1944 and a fracture in a similar location was found on the skeleton. Another item was the gap found between the front teeth in the mandible of the skull that corresponded precisely to that found in the SS dental records of Mengele's in Germany.
With these findings on June 22, 1985, Brazilian police formally announced to the press that the remainsy, "beyond any shadow of a doubt" belonged to Mengele. It was then that his family admitted they had shielded him all those years and they turned over his diaries and letters to investigators.