BERLIN, Germany (CNN) -- Police in Germany found six young men shot in the head outside a train station in the western city of Duisburg early Wednesday.

Four of the men were dead when authorities arrived on the scene. The other two died a short time later.
Shots were heard outside the train station after 2:30 a.m. (8:30 p.m. ET Tuesday), according to police spokesman Hermann Josef Helmich.
The victims were found in two vehicles.
Police have opened an investigation into the shootings, but do not have a motive in the case.
A pedestrian heard the shots and ""stopped a police patrol car that happened to be in the area,"" police spokesman, Reinhard Pape, told The Associated Press.
At about 2:30 a.m., police officers then found the two vehicles with the victims, all of whom were between 20 and 30 years old, Pape said.
Police sealed off the area and were working to secure evidence at the scene, he sai