I found out about this first thing this morning. I heard it was a brain annurism, but they still hadn't issued a definite statement. He was 43.
B5 remains my favorite science fiction TV series, and I have a deep respect for Richard Bigg's acting abilities. I was hoping they would do some more movies in the future. If they do, I guess they won't be able to have the full cast. It's an unfortunate thing to happen to such a kind human being.