Your heart is pounding rapidly in your chest, your palms are sweaty and cold and your breath is coming in a short, in-and-out rhythm.
The adrenaline is pounding. You open the door, drawing your weapon as you move. Your eyes sweep the room, and you see, THERE, threat!
As you shoot two rounds in rapid succession, you glimpse a movement out of the corner of your eye. You turn to see two threats swing out simultaneously from around a corner.
You fire into each threat as you smoothly transition through the room.