Sounds like he passed from a PE

. Probably had heart disease, then had flown the previous day and was, like most people sadly, unaware of DVT/PE, developed a DVT that traveled to his lung or one developed there. I don't know, speculation on my part. I wish this message about DVT/PE would continue to grow world-wide, to save lives or not live in a debilitating condition. Thanks to Dero, hopefully all that see and read this forum, pass our message along. Here's a link to an article I read about this.
http://weblogs.newsday.com/entertainment/tv/blog/2009/06/billy_mays_heart_disease.html