I am unsure if it the same for everyone (apparently it is not), however mine is:
If it different, or requires you to "activate" stuff, this is how you get it:
At the start of the mission, take the path up. You will see a generator linked to Glow sticks. There are 4 of these on the map.
Turn the generator on, a glowstick will light up, and somewhere nearby is a green spraypainted symbol.
A second generator is in a bathroom, stand on the spraypainted box and use a flashlight, or set a fire to see the symbol on the wall inside the bathroom.
A third symbol and generator can be seen from the stage where the boss spawns.
The final generator is behind a door that's locked. To get the key, there is a dead body Propped up against a pink… wall? It is in the silver lounge, the area under the locked door.
To open the security room, shoot the electric box OUTSIDE the control room, then go back and enter the code. The loot room it opens is all the way back at the spawn point next to the first generator.