From the Start head to the left. Than go to the second Floor. Go to the first room on the left on the second floor and wait until wave 10. Activate the Generator and take the Lift to the Catacombs by pressing the Caution Button.

One Player needs to interact with the Monitors. He is now able to interact with Doors, to open and close them. Close one Door in the Monitor Room and wait until Wave 12 to activate the generator for the Gun Room.
Only the Monitor controlling Player stays in the Room and the Rest of the Team heads back up with the Lift to the First Floor.
The Player at the Monitors makes sure to close both Doors to his Room, so he can stay there safely. WARNING! Sometimes the doors open automaticly, so make sure to check, if both doors are still closed.

CONTROLLING THE DOORS:
When the rest of the Team is near a camera, the player at the monitors can switch to those by pressing the left Mouse Button.
Open and Close Doors with E

Until now, no players with whom I played knew that, so I did not figure out where to go, but there must be a way out.

The red X shows easy to defend spots.

Wait at the Bottom of the Stairs until Wave 10 and than go up to the second floor.



On the second Floor go into the first Room on the left. Hide in the toilette or in the cineam till wave 10. Than head to the Elevator.