the washington post article kind of suggests to me they hadn't even put up a sign telling cars to stop?
It also quotes 15 people in the car and 10 dead (which is the number that was on the news here too):
To try to prevent a recurrence, Johnson ordered that signs be posted in Arabic to warn people to stop well short of the Bradleys guarding the eastern approach to the intersection. Before they could be erected, 10 people carrying white flags walked down the same road. They were seven children, an old man, a woman and a boy in his teens.
It also quotes 15 people in the car and 10 dead (which is the number that was on the news here too):
Fifteen Iraqi civilians were packed inside the Toyota, officers said, along with as many of their possessions as the jammed vehicle could hold. Ten of them, including five children who appeared to be under 5 years old, were killed on the spot when the high-explosive rounds slammed into their target, Johnson's company reported. Of the five others, one man was so severely injured that medics said he was not expected to live.