Two people were found dead on Thursday at a school in the town of Gosen-Neu Zittau near Berlin and a suspect has been detained, police said.
"Police received several calls reporting that a violent crime had taken place at a school. At the scene, emergency services found two people with fatal injuries," police said in a statement.
A 19-year-old German considered a suspect in the crime has been detained, it said, adding investigators currently assumed it to have been an act "motivated by a personal relationship".
Local newspaper Maerkische Allgemeine reported earlier on Thursday that one of the victims was an 18-year-old woman who attended the school and that the suspected perpetrator was believed to be her 19-year-old former boyfriend.
A 30-year-old man was killed while trying to stop the attack, the report said.
Separately, Berliner Zeitung reported that a further two people were injured.
Reuters