User blog comment:D. Cello/AC: Revelations Gameplay Trailer/@comment-3207949-20110818053025

The guard being killed in the last picture is Leandros, who is indeed the executioner from the trailer. I'm pretty sure that he gets killed at the beginning of the game, since he supposedly gives Ezio his first seal the gamespot article was vauge, it could be his last seal, so it either happens at the beginning of the game, or just after the harbour attack demo.