Last April 9th, at Dugway Proving Ground in Utah, two soldiers were driving a rented SUV about five kilometers from the part of the range used for live firing. It was at night, and an F-16 that thought it was firing at something in the live fire area, lit up the SUV instead. Only 70 20mm rounds were fired. Fortunately, the two people in the SUV were only injured (both from flying glass, the passenger got a dislocated shoulder as he rapidly exited the vehicle when it quickly turned off the road and stopped.) The investigation of how this happen has not been completed.
Link (with larger pic)