Police in East Westphalia are searching for a motorcyclist who shot at the Hertha Berlin team bus on Sunday afternoon.
One gunshot struck the windscreen of the bus, which was on its way to pick up the team from Bielefeld railway station ahead of their DFB-Pokal clash with the second-division side on Monday evening.
Hertha posted a photo of the damage to the windscreen on Twitter and appealed for witnesses, with their director of sport Michael Preetz relaying what happened to Sport1 television.
At the time, only the bus driver was on board.
"It was a gunshot, but we do not know what the motivation was behind it," Preetz said.
"The bus driver called the police immediately and they are now searching for the criminal.
"A motorcyclist overtook the bus first and stuck his fist up threateningly towards our bus driver and then drove at him around a roundabout and drew a pistol.
"Whether it was because he thought the team was on the bus or not, we cannot say. That would be pure speculation."
Monday night's cup game is nevertheless due to go ahead as planned.
"The team have seen the gunshot damage, but the biggest shock was to our bus driver," added Preetz.