Brake Abs Warning Light problems of the 2007 Toyota Avalon

During normal driving conditions, dry pavement normal traffic conditions,at approx 45 mph. With accelerator pedal depressed and maintaining 45 mph the brakes suddenly and violently applied. I do not know if it was front rear or perhaps both. Brake pedal was at no time depressed, braking was severe enough to cause the seat beat to lock up restraining driver. Abs warning light was on ( possibly being on prior to sudden braking but was not noticed if it indeed was). . Sudden braking lasted only for maybe a second or two then ceased and abs warning light went off with apparent normal braking operation returning for remainder of short trip. . . . Condition, thus far has occurred only one time.