Wiesenthal learned from a letter shown to him in 1953 that Eichmann had been seen in Buenos Aires, and he passed along that information to the Israeli consulate in Vienna in 1954. Fritz Bauer, prosecutor-general of the state of Hesse in West Germany, received independent confirmation of Eichmann's whereabouts in 1957, but German agents were unable to find him until late 1959. When Eichmann's father died in 1960, Wiesenthal made arrangements for private detectives to surreptitiously photograph members of the family, as Eichmann's brother Otto was said to bear a strong family resemblance and there were no current photos of the fugitive. He provided these photographs to Mossad agents on 18 February. Zvi Aharoni, one of the Mossad agents responsible for Eichmann's capture in Buenos Aires on 11 May 1960, said the photos were useful in confirming Eichmann's identity. On 23 May Israeli Prime Minister David Ben-Gurion announced Eichmann was under arrest and in Israel. The next day Wiesenthal, while he was being interviewed by reporters, received a congratulatory telegram from Yad Vashem. He immediately became a minor celebrity, and began work on a book about his experiences. "Ich jagte Eichmann: Tatsachenbericht" ("I Chased Eichmann: A True Story") was published six weeks before the trial opened in spring 1961. Wiesenthal helped the prosecution prepare their case and attended a portion of the trial. Eichmann was sentenced to death and was hanged on 1 June 1962.