I think it may be legit, but it may also be an optical / camera issue. For whatever reason, the frame before a very bright lightning strike can look a little wierd... I've captured bright lightning strikes on video, and I've sometimes noticed that there's a copy of the strike/bolt, but more faint and at a different location, before the actual ightning bolt that is capture in the video. For example, I'd see a very bright lightning bolt on a frame in the video (well, it's progressive video, but...). At times, I can back one frame, and I'd see the exact same bolt (the shape and features are identical), but much more faint at a different location (e.g. in front of my dash, etc -- so I know it's not a leader).
I think we've discussed this in a past, but I'm not sure where the thread is. If I could find the power cable to external hard drive, I'd pull a frame for an example. Not saying that is the same here, but just beware that it may be an artifact of the camera/camcorder (not sure how it works, but I've seen it before!).
EDIT: LOL Looks like I beat Adam's post below by several seconds... At any rate, we're thinking the same thing I see...
