dave: "all of a sudden there was like a bright green flash in the sky which then shot towards the ground. "
-- Sounds similar to something I saw in the summer of 1939 when I was a senior in high school and an avid amateur astronomer. What I saw was a pale greenish object, not dazzlingly bright but bright enough to catch my attention while I was already looking at the sky. It moved across the sky at speed that would be moderate for a meteor My guess then, and still is, is that what I saw was a bolide. I suspect that you saw a a type of bolide. There seems to be no universal agreement on the physical nature of a bolide. One suggestion is that one type might be an icy comet. I believe that that definitiion could have fitted what I saw and could fit what you saw. If it was an icy comet, not moving very fast, it could have appeared to have a circular disk and fade away as it evaporated. That's only a guess.