Triangular sighting in Central Denver, 10 May 2004, at 3:35 AM

Just wondering about this and tossing in my two cents in case any other confused Denver area folks contact you.
 This morning, at about 3:35 AM, I had a pretty amazing sighting.  I went out in the back yard for a smoke and, as is my habit, I scanned the sky while puffing away.  I noticed a star moving, then another near it.  After checking to make sure it wasn't illusory movement, I noticed a third.  Basically, it was a triangular formation, two lights leading with the third trailing them.  The formation came in from the south-east.  As if that wasn't enough, as the trio passed directly overhead, a fourth "appeared", joined the trio, and seemed to drop in altitude (perhaps because it definitely grew much larger and brighter than the other three).  The fourth came in from the east,  then changed course and speed to match the trio; the fourth partner sped off ahead of the trio to the north-east.  The trio followed slowly, taking about 3 minutes to cross the sky and disappear.
 (By the way, I say "trio" rather than "HUGE black triangle" because the stars only semed to dim and blur as the triangular formation crossed them, rather than completely blocking stars as I expect an intervening triangular vehicle would.)  Anyway, I was amazed and felt fortunate.  Nope, I wasn't inebriated/chemically-modified in any way (besides the nicotine).  Just amazed.
((ADDENDUM BY VIGILANT READER))
Please see the attached images for more details on the NOSS pass.
NOSS 2-1 (C) and (B) and (D)
USSPACECOM Catalog No.: 20691
International Designation Code: 1990-050-C
Observer's Location: Denver ( 39.7390°N, 104.9840°W)
                      Starts                     Max. Altitude            Ends
Date      Mag  Time       Alt. Az.  Time       Alt. Az.      Time       Alt Az.
 10 May  5.5  03:33:05   46  SW  03:34:57  87  WNW  03:41:21  10  NNE
((END))
We express our gratitude to the reader, who wishes to remain anonymous.  PD