Hovering object with circulating yellow and green lights slowly began to move before attaining hyper speed from virtual dead stop

While driving towards a remote and rural school pearched atop a small mountain ridge for an evening athlethic event in extreme northwest Alabama, my mother and I witnessed an object that appeared to be hovering just above (500 - 700 ft) the school that we were driving towards.  We were drving up hill and the winding road caused us to lose site for a couple different moments, but it became visable again each time our vision cleared.  
We could not see the school, but we could see how the night sky was slightly illuminated by the presence of the school and associated ground lights.  It appeared that the hovering object was observing the location.  The object appeared circular in shape (not round, but more disk shape).  There were slowly rotating lights that I beleive to have been yellow and green in color.   
After having watched this object and having seen it for a sustained period of time, and from different angles, there was no doubt that we were seeing an actual object and not any type of projected light or reflection, etc...
As peculiar and interesting as the sighting had been, what followed was most remarkable...  
I would suspect our distance from the scene to have been about perhaps a quarter of a mile, at the time.  We noticed that the object began to move slowly away from the ground illumination, and then, in a instant the object from an almost dead stop accelerated to an incredible speed that took it away from our vision in a fraction of a second.  It didn't just disappear, it disapppeared as a result of distance covered from our location.  We saw it go truly out of sight.  It left no light trail of any type whatsoever. What we saw was clearly visible and clearly trackable. 
It was a clear night and we had even discussed the event as it was taking place.  Our view was excellent for the sighting.  It truly looked like it was observing the mountain top scene, and simply left when it was done.  It's possible we spooked it off as we progressively drew closer to the locale with our car lights pointing in its general direction.
The event is etched in my mind and always will be.  I never gave much (and still don't) to the idea of it being extraterrestrial in nature, but it was without any question and unidentified flying object unlike any known then or today.