Detailed Explanation
Laura Palmer was killed by her father Leland Palmer, who was possessed by the demonic entity known as BOB. The truth is even more horrific: Leland had been abusing Laura since childhood while under BOB's influence, and the murder was the culmination of years of trauma. Laura's death wasn't random—it was the end of a lifetime of suffering at the hands of someone who was supposed to protect her. The reveal episode, "Lonely Souls," remains one of the most disturbing hours in television history.