Very large fly

I heard a very loud buzz, like that of an electric razor, in the bathroom. It was coming from this huge fly. I hurried to get my camera and managed a couple shots before it flew out the door. I found it on my bed, about a foot away from our cat. The cat didn't seem to notice and the fly stayed still while I took more photos. Then I took the fly outside and posed it on a piece of wood. One photo I took of just the head shows every segment in its large eye. The fly was many times the size of a house fly. It was about the size of a horse fly although it was not as long.