Before the male security guard arrived at the security room, Xu Shuo and the female tourist had already left via a small path, and were now opening the back door of the Haunted House.
The key to the back door was found in the muddy ground among the bushes.
After leaving, the murderer buried the key in the dirt, but the police had actually investigated this small woods and bushes as well.
However, the murderer had specifically come from the bushes near the "Rapids Advance" building and left that way, so the traces of the bushes being disturbed were all on that side, a distance away from the Haunted House.
It could be said that before and after the murder, the murderer was trying to wash away their own suspicion and cast the blame onto others.
After all, why not let someone else take the fall if they could?
After Xu Shuo unlocked the door, he first opened a small crack to peek inside, then turned back to the motionless female tourist and made a shushing gesture.