I was reading through the Assassin's Creed Brotherhood book when I found these words.
Page 132 lines 9 - 13.
I don’t know if this is legit or not as there are differences between the books and games. It’s either Ubi told Oliver Bowden how Ezio died or he made up his own way he died.At least Ezio had the satisfaction of knowing he could still win fights by using his wits and training - two things they couldn't deprive him of until the day they caught him and tortured him to death
I’d also like to mention that Ezio is still alive at the end of this book.