It turns out the helicopter Brian Williams was riding in DID get hit by enemy fire. CNN spoke exclusively with the pilot of Williams' chopper:

...Rich Krell, who was piloting the Chinook that Williams was on, tells a slightly different story than the crew members who spoke to Stars and Stripes.

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Williams was in the back of Krell's aircraft along with three other NBC staffers. Krell referred to his Chinook as the "second bird" in the formation. The "first bird," right in front of the "second bird," was struck by the RPG.

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All three of the helicopters were hit by small arms fire, Krell said, supporting Williams' past claims about that.

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The three Chinooks took evasive maneuvers. Krell's helicopter dropped off its payload, then met up with the other two about 45 minutes later. That may explain why the other crew members told Stars and Stripes that Williams arrived in the area later.