The guys in the helicopter made a mistake when the mistook the cameras for weapons, a tragic one but one that will happen in a war zone. They may have gone over the line when the opened fire on the van, since there where no visible threats at that point, but I don't know what the rules of engagement they where under says exactly.
The cover up was the military's claim that they didn't know what happened to the Reuters camera crew and that the attack made by the helicopter on that date was made on insurgents. Looking at the time line closer though, it does look like those two claims where made before the full military investigation was done. So it may be the case that the military took the helicopter crew's statements at full value before the investigation, and then after simply tried to say as little as possible once they realized the entire engagement was a mistake.
I've been trying to read the Centcom documents, but they seem jammed up today.
Jay