Mysterious BOOM and a bright flash of light across the sky in Washington State A mysterious boom and a bright flash of light across the sky are puzzling emergency-management officials in Washington state Wednesday night. According to the Grays Harbor County Emergency Management department, numerous people reported the sound and beam of light across skies along the coast and as far inland as Montesano before 8 p.m. Some even said their homes shook. A mysterious boom and a bright flash of light across the sky are puzzling emergency-management officials in Washington state Wednesday night. According to the Grays Harbor County Emergency Management department, numerous people reported the sound and beam of light in the skies along the coast and as far inland as Montesano before 8 p.m. Some even said their homes shook. The department quickly contacted the National Weather Service in Seattle to see if any severe weather was to blame. But the cause of the event remains unknown.