Other mistake: When we are first introduced to Leland Palmer and Benjamin Horne, they are discussing a contract in front of a large, lit fireplace. A couch (on which Leland is seated) is in front of the fireplace. Strangely, the flames of the fire are visible through the couch, and also Horne's legs are at one point. (00:11:09)
Other mistake: When Cooper is on the floor after being shot, as he's signing the check, he is doing so with the pen closed, and proceeds to click it open as he hands it back to the room service.
Chosen answer: Laura was killed by her father Leland, whilst he was apparently possessed by the spirit BOB. The exact manner of her murder is not clear, as several injuries found during her autopsy we later discover occurred during a separate incident before her murder. We know that she was beaten and killed in an abandoned train car, and her body was then wrapped in plastic and thrown in the river.
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