At one point of the video you can see the tiniest bit of his error sign peaking into the door, there is no way of knowing how much more he could have seen. Because he was right next to the door at one point of the video. So there is a chance that could have been him retreating back after watching you kill the man to get a better shot at killing you in a straight hallway.

At one point of the video you can see the tiniest bit of his error sign peaking into the door, there is no way of knowing how much more he could have seen. Because he was right next to the door at one point of the video. So there is a chance that could have been him retreating back after watching you kill the man to get a better shot at killing you in a straight hallway.