During an operation in the station district of Frankfurt am Main on Tuesday morning, a young man was fatally injured by a police officer's shot.
According to the public prosecutor's office, he was seriously injured during the operation with special forces and later died.
Before that, there should have been a threat of some kind, it said.
The investigators initially gave no information on how many shots were fired and how exactly it came to be used.
The road was closed to traffic by police after the shooting.
There was also no information about the identity of the young man.
Frankfurt's new chief of police, Stefan Müller, recently announced that he would improve conditions in the station district.
He sees a “multiple problem situation” there.
Police officers often take up arms.
In June, for example, an officer seriously injured a 25-year-old in Berlin.
The man attacked the police officer and stabbed him in the face.
The attacked fired several shots and injured the 25-year-old in the stomach, among other things.
In March, a police officer in Mainz fired several shots, injuring a 32-year-old.
He attacked three men with a knife in front of a driving school in the city center.
The official had recorded a traffic accident in the immediate vicinity and rushed to help.