At the end of Dark Knight Rises, we see the twist of Bruce/Batman taking the bomb himself across the sea, presumably, to sacrifice himself to keep Gotham safe.
We know this isn't the case for Bruce Wayne is very much alive. Only Batman, is known as dead to the general public. We see at Bruce's supposed funeral, only Gordon, Blake, Fox and Alfred are present.
However, what is the reason the public knows Bruce to be dead, without revealing his identity to those who already know?
It is said on wiki that he is presumed dead by the riots, but that is never stated anywhere implicitly whether in papers of the movie, or by any character, nor is this referenced anywhere.
Is there anything official stating why Gotham thinks Bruce Wayne is dead, without assuming he is Batman?