Cohen's Room *possible spoilers*

[mgoeclipse]

Where's Cohen's room?
I waited till he came down the stairs, then opened that case before I killed him. I took his picture, and his key (so I could open the chained case), but can't find his apartment. Is it in the same area/building where you do all of his missions? Or will I just run into it in the course of the rest of the game?

[Lunacy182]

You can't get to his apartment if you kill him. You have to let him live. If you still want to get to his apartment you have to reload a save before you killed him.

[K00PA TR00PA]

To enter cohens room (later in the game in Olympus Hieghts) you need to keep him alive. So if you killed him at fort forlic and didnt save before then, youre going to have start a new game.

[The Pants Party]

Been discussed quite a bit, I'm sure you would have found your answer with a browsing of the Achievement Guide or Achievement Discussion threads...

Let him live after you've finished the masterpiece. His house is at a later level, in Olympia Heights.