dude, where are the Armored guards with the big guns? and the other thing, why not show a sneaky and stealthy way to complete this mission? killing everyone seems like the obviously easy way..
@123herberti: Diana. If you notice, at the end, when 47 is looking at Victoria through the sniper rifle. Diana is behind her, and says; "Do what you have to do." So, shes not really dead.
The last words heard in the game (before the pre-credits cutscene) is Diana saying, "Excellent work, 47. The money has been wired to your account. Welcome back...and thank you."