One person was killed and four others injured after two helicopters collided while taking part in a police training exercise in the German capital Berlin.
The accident occurred at a very low altitude in dense fog and snowfall near the city's Olympic Stadium.
Helicopter debris showered onto a sports field next to the stadium seconds after one of the helicopters had taken off from the spot.
Houses and schools are located nearby.
Germany's Bild daily said on its website the dead person was one of the pilots.
Hundreds of police officers had been taking part in the training exercise at the stadium, designed to help them deal with soccer hooligans.
Many of the participants were playing the role of hooligans at the time of the crash.