Same thing happened to my family about 12 years ago. There were nine of us in the house on three different floors and a huge flash of light was seen by all of us. It was just a big flash along the whole ceiling of the main floor and then the kids all came running from the basement and the third floor describing the same thing they had just seen. I will never forget it. This happened during the day but the flash of light was so much brighter then anything outside coming in.