Josef “Sepp” Gerg, a 33-year-old farmer in the Gaißach region of Bavaria, blew himself up in front of his fiancee Anne S. and seven friends, daily Bild reported.
Gerg, a trained fireworks operator, had made his own device consisting of five tubes, each filled with explosive powder, welded to a metal plate.
Around midnight, he set the device to detonate on the footpath. The friends all retreated to a safe distance of about 15 metres.
The first two tubes exploded but the third failed to ignite. When Gerg approached the firework and bent over the third tube to investigate, it suddenly ignited. He suffered serious facial injuries and died at the scene.
Gerg was the brother of former slalom skiing champion Annemarie Gerg and also the cousin of Hilde Gerg, who won a gold medal in the women's slalom at the 1998 Winter Olympics in Nagano, Japan.
Annemarie Gerg took 2nd place in Slalom in Val d'Isere World Championships in December 2006 and competed in the Turin Winter Olympics in 2006, but retired the following year with a knee injury.
The mayor of the municipality of Lenggries, Werner Weindl, said: “The family has been hard hit. The whole area is shocked.”