Mission: Berlin: Apex Predator
The first step to complete this is to get to Hirschmuller's office (Level -2). This can be done through a series of disguise changes or sneaking around.
Once here, use the gramophone to lure Rolf to the corner of the room. Take him out, hide him, grab his disguise, and pick up his phonebook.
Now, use the phone to call a meeting with the ICA agents. Sit down in the chair, and wait a few minutes for the meeting to conclude. Upon concluding, 5 total agents will be in the room. Agent 47 will kick over the desk, and you can grab a shotgun. Use it to take out all the agents, and escape the level.