I echo Mighty God King's statement: God damn it! For those of you who do not know, Dwayne was a comic book writer born in Detroit, who expanded into animation, working on the Justice League Unlimited series and who was writer on some of DC's recent direct-to-DVD animated movies. His last work was an adaptation of Alan Moore's All Star Superman. No one knows at this time what he died of.
I am very upset at this. McDuffie was a very talented writer and by all accounts a great guy. For more details visit Comic Book Resources.