Fast moving, bright shimmering rectangular object near Elma WA in daylightOn 9-10-16, apx. 12-1210pm, while on my daily walk, I saw a large, shimmering, fast moving, rectangular shaped object for 3 to 5 seconds.The sky was clear blue, cloudless, windless, sun up and shining. I was near Utility Lane, Elma, Washington, walking eastwards. Elevation is about 300 ft. The object appeared to head from Northerly direction east of ELMA to a Southerly direction towards Oakville, over the tops of hills that are about 500 ft in elevation. After about 3 seconds, it turned to a black color, and dropped in altitude, and became obscured by a closer hill. Never saw object again. Did not hear any sound.Unable to determine distance and size of object from my vantage point.Speed was significantly faster than a standard prop plane. Also, there were no noticeable aircraft flying even though there is a small airport nearby, and this is in a flight path for military aircraft as well as SEA-TAC International airport. I've seen many planes, ultralights and helicopters on a near daily basis in the area, over many years, and this was not one of them. The only reason for this report is the extremely bright shimmering, approaching a welding arc color in brightness. Difficult to look at. Even aluminum skinned planes aren't this bright! As a side note, I mentioned this to a friend in Oakville, WA. She was on the phone to a friend in California when she heard a sudden thundering sound that somewhat echoed, and was gone as fast as it started. She heard this about the same time as I witnessed the object in question, from my location about 15 miles away. It may or may not be related.