When the identity of the Origami Killer was finally revealed, most people were in shock. They could not believe that one of the four main protagonists was the main antagonist from the beginning: Scott Shelby. Up until that point, he came acoss as a warm and compassionate man, especially during the diaper-changing scene. Not to mention, the player could read his thoughts! It shouldn’t have been possible to miss such an important detail. But, Quantic Dream was slick about the ambiguity of Shelby’s inner dialogue.
What people tend to forget is that Scott Shelby being the Origami Killer does not make him a heartless person. As screwed up as his actions are, his mental state is far worse. It’s what makes him one of the most complex video game characters ever conceived. The reason why Shelby never demonstrates regret for his actions is because he truly does not blame himself for their deaths. He blames their fathers, and his own father even more for letting his brother die. If you play the game so that Madison is the only one that shows up to the warehouse, you get the biggest look at Shelby’s motives, and how he justifies himself: “Every child that died, it was as if my brother died again.” He kept recreating the scenario as a way of playing it back over in his mind, until he achieved the result that he wanted.
Ethan Mars was Shelby’s last ditch effort at freeing himself from his own inner turmoil. Shelby suddenly remembered that the man that jumped in front of a car in an attempt to save his own son (which inspired his actions as the Origami Killer in the first place) had a second son. He wanted his actions as the Origami Killer to end as much as anyone else; perhaps even moreso. Shelby arguably had more remorse for the children that died than most of their fathers. Case in point: When Shelby visits Reza, it’s obvious that he either did not attempt or simply gave up on the trials, yet he blames the police for his son’s death. Not to mention, he refuses to help Shelby catch the Origami Killer because his own son is already dead. So, why bother preventing anymore from dying, right?
If Ethan is the only one that shows up to the warehouse, Ethan pulls a gun on Shelby, who says: “Go ahead, you can kill me now. It doesn’t matter anymore. You’ve accomplished what I wanted to see.” If the player chooses to shoot Shelby, he falls to the ground with a smile on his face. Shelby did not want to live with the realization of what he had done, or the pain that he had carried his whole life.