Follow the path until you see the patient who's talking to himself. Now go to the left and enter the first door that you see.
Inside you'll see some patients being chased by the black smoke. You're safe for the moment.
Go to the direction on the opposite side of where the patients went to and keep following the corridor. Enter the very last door in that corridor.
Inside the room turn left and you'll see and open door with a lot of computers inside.
Go near the radio and interact with it. A cutscene will start to play.
As you exit the computer room this guy will throw someone at the door and break it down. Hide somewhere in the dark and wait for him to get away from the door. It's easier to just run from him than it is to hide from him.
Once the door is clear make a run for it and turn on the first corner. You'll see a guard locking himself in another room. Take the first corner as you won't be able to get in that room anymore.
Vault over the table and towards the other side of the corridor. Turn left and keep running.
Inside the next room run to the left side and you'll see an open door. Quickly go past it and vault over another table that's in the way.
And finally get through the narrow gap in the barricade. You'll be safe once you get through it.
Enter the door that you'll see as soon as you get past the barricade. There's a battery inside and you'll also hear a broadcast. Now we need to get to the administration block.
Go towards the corridor on the right side and enter through the gate. You'll find a man writing something on the wall. Further down the path you'll find a hole in the ground. Jump down through it.
First look towards the left and enter the door that's ajar. Grab the documents inside, it's on top of the table.
Now leave the room and head towards the exit sign. Inside the next area there are some guards. Get around the office area there's another open door here that leads to another office room. Grab the battery on top of the table and exit the room.
Directly in front of the office door there's an open gate. Go through it and keep walking until the game auto saves and you get chased by the big guy.
Run to the left and go around the corner. Don't stop just keep running.
You'll have to vault over two beds. The path is straight but there are corners that might seem like you need to turn but ignore them. You have to go straight down the path.
After you pass the wheelchair you'll notice that the path is blocked. Don't panic and look towards the right side where the curtains are fluttering. The window is open and you can use it to exit the building.