532nm Light From Skky

On Dec 6th, around 20:00 me and my wife were sitting in our apartment building when the power flickered. This went on for about 15 sec. before I went to balcony to see what was going on. Then I noticed something I cannot explain. A very wide aqua green light coming down from the sky. Let me note here that I live on putty hill which is one of the highest points in the city. There was also a low cloud coverage. This light  seemed to be powering up cause I could here a humming sound, and then a very bright beam would illuminate the sky.