Black triangular object flying low over Brookline MA in August 1987. Made no noise, had no lights.

I was lying on the roof of a building on a warm summer night.  It was very hot and hazy, to the point where stars were almost not visible because of haze and heavy light pollution from street lights.  As I lay on the roof looking upward a black triangular craft moved right over the building just above me.  It was about 150 above the ground and was completely black.  No lights, but the bottom of this thing was illuminated by the light pollution from the street lights on Beacon Street.  It was clearly a triangular, black object and I wouldn't have seen it if I wasn't lying on my back on a roof!  It was completely silent.  Made no noise whatsoever, and it was only about 100 feet away.   I was too dark to make out any other features.  It was not a conventional aircraft.  Don't know what it was.
Witness indicates that the date of the event is approximate.  PD