"Last time I checked, US soldiers do not carry the AK-47 (except, perhaps, as a war trophy)."
Yet, AK-47s are fairly available in that theater. I'd guess that someone wanting to disguise a murder might just use one, instead of his issue weapon.
This case is not over. Right now, they're just deciding whether to hold a court martial. As always, I will withhold judgment until the case is concluded.
Green, on the other hand, is not exactly what I'd call a stable person, based on articles about him.
We shall see. But the AK-47 thing is easily explained.
Semper Fidelis