How did this accident happen?

At least 11 people died yesterday when a train struck a bus on a level crossing in Russia’s Baltic enclave of Kaliningrad,the Inteffax news agency reported.
    Anatoly Ktimov, deputy head of the local transport police, said an initial investigation indicated the bus went past a stop sign at the level crossing and was hit by an oncoming train.
    Nine bus passangers were killed in the Collision, near the village of Ow’azhroyc in the Kaliningrad region. Two more later died from their injuries and 17 were being treated in hospital. It was unclear whether the driver was among the victims.
    "It is difficult to give the precise number of victims because there are a lot of body parts at the scene, and their identification will be difficult," Klimov said.