Burke reacted very oddly when Dr. Phil asked him if the note looked like his mother's handwriting. He didn't didn't really vehemently deny it. He picked one phrase, at the beginning of the document when the writing is most disguised, "Listen Carefully", and said it stood out as not appearing to be her writing. Strange. Simplest theory: BR woke JBR late to go downstairs and play with some toys. They ate pineapple together. He plays with train set, she annoys him, he jabs her with it. She threatens to tell on him, he hits her with flashlight. He thinks she's dead, tells parents. They think she's dead, panic, fear for son, stage ridiculous cover-up. Once police bought the kidnapping, they couldn't/didn't turn back.