IMO, the longer this goes unsolved, the less likely the shooter was unhinged. Mentally disturbed people are usually known to have hated their target, they make mistakes during the crime, confess to someone or act suspiciously, or do something criminal again. This seems almost professional: done when the victim would be outside so no need to break into the home, done when it would be dark with no one else around, pulls up to park without even driving past to scope out the scene, so they must have been watching beforehand (how did the killer know there wasn't someone helping her set up the sale?), completely deliberate killer who took repeated shots with successful aim, who had the presence of mind to immediately run back to their car, and drive away without getting into an accident. Astonishing self-control. I'm not so sure Elizabeth saw the gun: I think perhaps she jumped back because the woman suddenly appeared in front of her, but she doesn't keep backing off as you'd do if a crazy person confronted you carrying a gun. The way the killer showed Elizabeth something may have just been a way to distract her and draw her closer, so she wouldn't have a chance to run away. I have a very hard time seeing this as random, and yet why would someone sane take this enormous risk to kill her. Maybe love, or maybe money.