"The US Army claimed the Italians' vehicle had been seen as a threat because it was travelling at speed and failed to stop at the checkpoint despite warning shots being fired by the soldiers. A State Department official in Washington said the Italians had failed to inform the military of Sgrena's release."
Seems like they were pretty stupid to run a checkpoint at a high rate of speed. Prosecute the driver.
An account a few days ago said the American soldiers were shooting at the engine of the vehicle. That might explain many, many rounds expended.