Juergen Kiessling, 65, was rushed to hospital from his house in Reinickendorf, a suburb of Berlin, after a neighbour heard the shot.
The motive for the apparent suicide attempt is not yet clear.
German media report that he left two suicide notes - one for his daughter alone, and one for his family.
Berlin hosted the World Cup final on Sunday, when fans watched Italy beat France on penalties.
Mr Kiessling was known as "Mister WM" (Mr World Cup) by colleagues in Berlin. He was responsible for the hugely successful Fan Mile in Berlin city centre, a concourse where giant screens showed the matches to hundreds of thousands of fans who could not get tickets.
The tournament was widely seen as a great success for the host nation.
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