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 incident is not clear, but reports said Mr Kiessling left two suicide notes.
Berlin hosted the World Cup final on Sunday, when Italy beat France.
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.
Mayor Klaus Wowereit said Mr Kiessling had worked tirelessly, and praised his "great and successful commitment to the World Cup".
The tournament was widely seen as a great success for the host nation.Last Mod: 20 Eylül 2018, 18:16