Wiper problems of the 2007 BMW 335

I was driving on I-405n at around 70 mph, the pace of the very light traffic that night, and there were no other cars within 100 yards in front of me. There were no overpasses or pedestrians anywhere nearby. All of a sudden, my sunroof spontaneously shattered! a large piece of it broke off and then was blown backwards, bouncing off my roof and trunk, scratching the paint. The person driving behind me drove over the sunroof and shards of glass. Luckily, I had my sunroof sunshade closed which prevented the shards of glass from showering on me when the sunroof exploded.