User blog comment:Suriken88/Ezio's speculated death in Embers/@comment-3183702-20111219103719

You know... poison can actually accelerate/trigger an heart attack. He was already old and sick yeah, but just a small bit of poison would probably be enough to die in that state... I think there's no 100% way to be sure he wasn't poisoned in my opinion. It's up for debate and I think it will always be, ufortunately.

Poisoned or not, there's no doubt the guy sitting next to him was a Templar... http://assassinscreed.wikia.com/wiki/File:Templar_Embers.png