Supposedly, they were very closely spaced, indicating they were fired from very close (notwithstanding the medical report which was fudged after the action) although this by itself proves nothing. In the confusion of battle, friendly fire can just as easily come from the guy standing next to you as from someone a mile away.

And he wasn't necessarily shot because he was anti-war, he may have been fragged for being too gung-ho by someone who was anti-war, or for personal reasons that had nothing to do with politics.

In short, nobody knows what happened. All we do know for sure is the Army tried to cover it up. With all this attention from the press, the truth will come out eventually. Be patient. And don't make fools of yourselves trying to figure out what happened based on your political prejudices.