Jett Travolta apparently dies from head trauma after suffering from a seizure in his bathroom of the family's vacation home in the Bahamas.
TMZ.com has an article about it here: http://www.tmz.com/2009/01/06/jett-travolta-found-with-pulse/. The article adds new information stating that Jett was found with a weak pulse.
Bild.com has an article here: http://www.bild.de/BILD/news/bild-english/celebrity-gossip/2009/01/06/john-travolta-son-jett/died-of-epileptic-fit-reveals-autopsy.html. This article says that Jett died from an "epileptic fit."
There is another article from omg.yahoo.com; this article is an interview with the Travolta family attorney as well as John's attorney. That article can be found here:http://omg.yahoo.com/news/family-lawyer-jett-travolta-may-have-died-in-fathers-arms/17139?nc.
Finally, you can read the press release of the immediate family by clicking this link: http://www.travolta.com/. It is the link to John Travolta's official web site.