After looking through my reference books and a quick search on the net, I couldn't find anything that resembled this insect. Doug sent a few more photos with a little better look at the wings. Finally I sent the photos to Kao asking if anyone down at the visitor center knew what it was.
Here is what Kao said: The insect is a species of Deer Flies.
One of the things that bothers me is the size, the deer fly is a little larger than a house fly but we'll let Doug comment on that since he's the one that saw it in action.