This is an hint for the last part of the game when you 
have to defeat Sam. 
Right after the cutscene you are behind a pillar. 
Now you can run into the hallway where you came from, 
while you do that Sam will try to shoot you. 
Now you can turn right and walk to the edge, 
if you look to the other hallway you'll see Sam. 
Sam will turn around about every 20 seconds, each time he 
turns his back towards you, you must shoot Sam in his back 
and hide behind the wall before he turns around. 
Do that till Sam walks away, then take your shotgun, follow 
the blood trial and shoot 
Sam as he appears. Now you'll see the final cutscene..... 
Submitted by erikhop