This simple question indicates whether or not you have the mind of a killer (I would assume most people here do)
"A guy was attending his mother's funeral. While he was there, he met the most beautiful, funny, apparently rich girl he'd ever met. They talked for hours, and the guy fell madly in love with her. After the funeral, the guy realized that he had never learned the girl's name. The next day, he murdered his sister."
Why did he murder his sister?