Growling? who started it?

Possessed - The Beasts of the Apocolypse : great stuff

I would agree with Lee B. on this one, as this goes back to the early 80's.
 
Jeff from Possessed also comes to mind first. Possessed was probably my introduction to death metal back in the mid-80's. Check out Seven Churches and Beyond the Gates to see death metal in its early stages.
 
good question but i recall it was from a somehow reliable source...still i believe mantas was earlier than almost anything thats why a lot of people venture to say chuck created death metal...i dont i was 4 years old at that time