Only witnessed A bright 2 second flash of light from inside the house and the house shook about 20-30 second thereafter.Was inside of the house getting ready for the day, When witnessed A big flash of light that lit up the entire sky & surroundings. The area was visible for about 2 seconds. Did not witness anything audible, only that bright flash of light. Approximately 20-30 seconds later, the whole house shook, something like A sonic boom without the boom. We live in A place called Lawai Valley Estates in the very bottom of the valley, South Kauai, about 7 miles from the ocean.