It was completed by his pupil Franz Süssmayer after his death, which occurred in Vienna, Austria, on December 5, 1791.
On concluding The Magic Flute, Mozart turned to work on what was to be his last project, the Requiem. This Mass had been commissioned by a benefactor (financial supporter) said to have been unknown to Mozart, and he is supposed to have become obsessed with the belief that he was, in effect, writing it for himself. Ill and exhausted, he managed to finish the first two movements and sketches for several more, but the last three sections were entirely lacking when he died. It was completed by his pupil Franz Süssmayer after his death, which occurred in Vienna, Austria, on December 5, 1791.