From what the news reports are saying, and as you can read from Mays' own Twitter (his last), he was on the U.S. Air flight to Tampa that blew a tire on landing yesterday. Items were flying around the cabin, and Mays reported to a local TV station that he was hit hard on the head by something during the landing, but laughed it off. Coincidence? Sounds very possibly like a delayed reaction to a severe brain injury to me, much like Natasha Richardson's unfortunate accident. (Do read Mays' Twitters. They show a nice family man with a very friendly outlook on life. Really poignant to read them now.)
Billy Mays was clearly a memorable part of the current television landscape, and we offer our sympathy to his family, friends and fans.