Alicia Domon, Caty, (September 23, 1937 – December 17 or 18, 1977) was a Roman Catholic nun from France who was one of two French nationals in Argentina to be "disappeared" in December 1977 by the military dictatorship.(...) That group of detainees, including Sister Léonie Duquet, was "transferred", a euphemism for being taken out and killed. Bodies washed up on beaches south of Buenos Aires in December 1977 and were quickly buried in mass graves, but a March 1978 Agence France-Presse article reported that the bodies of the missing two French nuns and others associated with the Mothers were believed to have been among them.

Just the first googled thing.