EE stated he was walking to his Shuttle car when a small piece of rock fell from the roof and struck him on his head and neck. Rock was 1-1/2"" thick X 11""W X 29"" long. It broke into several pieces.EE has had a possible broken neck some years ago and the MRI showed Severe Degenerative Disc disease at C6-7. Also mild dextroscoliosis at C1-2 level. ILLNess.