The hornets were gathered in their nest in a tree trunk but it's not known what triggered the stinging frenzy. Hornets can be dangerous, particularly to people who suffer from allergies.
Hornets, which belong to the family of wasps but are slightly larger, are a protected species in Germany and their nests may only be moved with official approval.
Both hornets and wasps are very common insects during summertime in Germany. People are advised not to make sudden movements around them or disturb nests to reduce the risk of receiving a nasty sting.