I think it's a pretty sure thing at this point, but for what it's worth, CNN still hasn't confirmed it, they're just reporting that others (LA Times and AP) are reporting it:
"CNN has not confirmed his death."
edit: they're now reporting on the broadcast that they have just confirmed it.
The last tweet about it is 14 minutes ago. The search page was refreshing with 1000 new tweets/5 seconds when I first heard the news. This is such a hot topic that Twitter can't keep up!