The boy’s mother and 9-year-old sister were seriously injured in the incident and were taken to hospital after receiving emergency treatment at the scene, a police spokesman told Deutsche Presse-Agentur.
Authorities said the violence began inside a residential building before spilling onto the street, where the boy died despite immediate medical intervention.
Police said a homicide investigation has been launched and no further details on a possible motive were immediately available.
The suspect remains in custody and is expected to be brought before a magistrate.
The area around the building has been cordoned off as forensic teams continue their work.