Long Description of Sighting Report

While enjoying a nice sunny day in Denver, 12/2/08, and as a 76 year old photo hobbyist who for ten years was a Navy photographer I photographed a Pulsed Contrail above South Denver's Washington Park Lake. Almost always carry a camera with me for an event like this. Just above, and to the right, of the pulsed contrail I saw a small object making strange, rapid, unbelievable maneuvers. It moved very fast and turned extremely fast,changing it's perspective, then it disappeared behind the clouds or I would have taken a picture of it also... Not a bird, nor a plane could maneuver like it did. While I was pointing my camera at the sky none of the joggers running by me along the side of lake looked up, or asked me what I was taking a picture of...