Having worked with the USAF on many occasions over the years I am sadly not surprised when incidents like this happen
Having served in Bosnia (Norw. Army) alongside US army peacekeepers, I'm not surprised.
There was a incident when AH-64's engaged other SFOR troops (fench i think) during a live fire ex. on a "bush" range, none was injured, thanx to poor targeting by the US pilots. (The AH-64's was not in the exercise, they just overflew the range)
"Oh- a man with a gun, bullets flying, not in US uniform, lets fire on him"
They know where their own are, but not anyone else