I don't understand either. Why the probe?
If this was a friendly fire accident ..these things, unfortunately, happen somewhat often, no?
Or are you insinuating this was a deliberate murder of Tilman?
If that is what you are implying then --it was only one single terrible individual who it would reflect badly on --as it should.
Please explain.
It might not be murder, which implies premeditation and intent, but something like "criminally negligent homicide". Perhaps someone blatantly disobeyed an order or violated the ROE and that is what resulted in Tillman's death.