One person was killed and three others injured in a shooting at the Grey nightclub in the German city of Konstanz in the early hours of Sunday, the German police said in a statement.
The gunman was shot dead by police in an exchange of fire that has also wounded a policeman.
"Many guests had left the building panic stricken or were hiding when the shots were fired," the statement said.
The gunman was a 34-year-old Iraqi who has lived in Germany for a long time, Fritz Bezikofer from the Konstanz police told CNN.
"According to our investigations this is not terror-related, unless the gunman radicalized himself within the last three days," Bezikofer said.
"At this moment we believe that he may have had alternative motives," Bezikofer added, without providing further details.