The C4 detonator is in the room just south of the Operations Room, sitting atop a desk. To reach that room, players will need the Cutting Tool found outside the Art Room on the second floor of the ...

In this room is the C4, and you can use the detonator with the C4 to arm it. Stand back behind the nearby bookshelves once you’ve armed the detonator, as it’ll go off in exactly 10 seconds.