Not sure what the cause of death is. One thing is for sure, for an "unknown" actor, Rebhorn has certainly left some memorable roles behind.
http://movies.yahoo.com/blogs/movie-news/james-rebhorn-dies-65-181324318.html
EDIT: Apparently, he had melanoma.
http://movies.yahoo.com/blogs/movie-news/james-rebhorn-dies-65-181324318.html
EDIT: Apparently, he had melanoma.