I was sitting in my living room watching tv and at just before 9:00 pm i heard a loud helicopter approaching. this was unusual so i hurried outside the side door of my house to see what was going on. it was pitch black out and besides some scattered clouds the sky was relatively clear. i heard the helicopter coming from ene direction but it was still behind the treeline and i couldn't see it yet. a few seconds later, something caught my eye to the east at about a 45 degree angle. i thought my eyes were plying tricks on me but i swear i saw a dark "something" moving through the sky in a sw direction. i was able to detect the movement because it blocked out the stars in the background as it went along. i didn't think much of it and my attention turned back to the approaching helicopter which i still couldn't yet see. just as the running lights of the helicopter came into view, a pale red/pink light appeared to my ese (same flight path as the dark "something") and i thought it might have been a satellite. then i looked back at the helicopter. i couldn't tell what kind it was but it was big and loud, shaking the house, and flying at what i'd guess an altitude of 500-700 feet. i turned my attention back to the pink ball of light and i realized that it actually couldn't be a satellite because it was moving across the sky too quickly and the flight path was slightly curving to the south. before they went out of view behind the treeline to my south, i could tell that the helicopter was a few hundred feet behind the light and it appeared to be chasing or following it. even though the pink light was small, it definitely had mass to it. almost like it was another aircraft that was running dark and not using any conventional navigation lights. besides the sound of the one helicopter, i didn't notice any other aircraft type sounds. i'd estimate that both aircraft were flying at around 80-100 mph. why would a large helicopter be flying extremely low over a residential area at 9:00 at night? the pink light obviously had something to do with it.