NO
That's the short answer to this question , as of midnight (June 4th) There's been a huge wave of traffic towards this question , so I can say with a firm answer he's not dead.
On another interesting note though , It's been confirmed that he did not write his song "pants on the ground" and is in quite a bit of hot water as to who's going to make any money from it. I feel bad for the guy , he seems pretty good. The report of him being killed has something to do with another report that E! Published about him being robbed. It sounds more like a bad game of telephone to me where it started with ' Larry was robbed' and ended with 'Larry is dead'.
As another interesting facet of the Larry Platt story , he will be performing on American Idol in the coming weeks with a performance and Crystal Bowersox will be on there too!