I was talking to my wife on the phone, who happened to be about 4 cars ahead of me on the freeway. All of a sudden there was an explosion, then glass shards fell down on me. (still have small glass slivers in my hands and head)

My wife heard it on the phone, looked back and saw glass blowing off my roof.

Either:
Something fell from the sky and hit the sunroof.
or
Fatigue in the glass or frame put too much stress on it and it exploded. ( <-- best guess )

... let's just say my black interior almost turned brown.