It appears that there was an attempted assault on the Dutch Royal Family. An unidentified man drove through a crowd likely trying to hit the bus the Royal Family was riding on. While he missed the bus, five people from the crowd are now dead.
Video embedded below. (from http://gatesofvienna.blogspot.com/2009/04/attempted-regicide-in-netherlands.html#readfurther)
More at http://edition.cnn.com/2009/WORLD/europe/04/30/netherlands.queen.car/?iref=mpstoryview.