because US owns the skies and, unless it was artillery, which it's hard to believe wasn't distinguished, one has to presume it's coalition air support. like Gulf War I it's ironically tragic how many casualties are self-inflicted friendly fire or due to accidents.
They mentioned artillery the other day. I'm pretty sure they'd know the difference, but since it's BBC that's reporting it, I'd like a little more info. If the planes were seen, then that would probably indicate a friendly fire bombing - but if the planes were called in to take out an artillery position and a mortar got lobbed in under them, it might be hard to distinguish.
I'm not trying to be cynical, I just want a little more info and the facts are a little lean in the story linked...