The latest info indicates he died almost instantly after *removing* the broken-off spike from his chest. But they can't say yet whether it was the venom or damage to his heart.
There is complete footge of the entire incident
Hopefully taste and decency will ensure it does not make it onto the internet...
It might be a little hard to explain to you guys over there in the US, but it is extremely hard to become a "hero" over here - where a pretty hard lot to impress. Steve Irwin is one of the few universally liked non-sports heroes we have. We'll take the loss hard.