The fire alarm goes off like any other fire alarm. Then the automated system cuts in.
"May I have your attention please, a fire emergency has been reported in the building. While this is being verified please leave the building by the nearest exit"
The droning automated prerecorded voice echoed repeating itself as you shuffle twords a exit.
A more serious alarm kicks in blaring as the power flickers in and out blast doors sealing. A explosion is heard close in the building as the floor shakes violently.
A reel to reel computer crashes over as the shaking continues ventilation crashing down getting caught in cables, pipes bursting.
In the distance you can make out a muffle evacuation siren no doubt the one in the near by city.

then the doors bust open and you get eaten :v
If I had the power to animate Id so develop this into a short movie, I love adding sounds an ect.

I supose you can say this takes place after this Brake Failure"Incident" COMIC link
They probably managed to capture this mutated monster and tried to use it as a source of power....which doesnt work out...