Shots were fired at a German school in the northern city of Bremerhaven on Thursday and one person was wounded, police said.
One person was detained after the shooting and the injured person was taken to hospital, they said.
German paper Bild had reported that a second suspect was on the run, armed with a crossbow. Police said they were looking into whether more than one person was involved.
The shooting took place at the Lloyd Gymnasium, Bild reported.
Online newspaper Nord24 said a schoolgirl who heard shots had called the police. Students barricaded themselves in their classrooms, it added.