So, the maker workers did not know that their boss would not be upset by the organ harvesting, that is why it was done in secret. The doctor was shot because he had already been given secret information that had compromised the rules of the game. (Which means something important to the leader.) Also, the doctor had glimpsed "behind the curtain" and seen a lot of the workings of the Squid Game and may have known too much. If he passed on the things he knew to other players, who knows what could have happened. The leader needs absolute control of the players or the game won't go.as planned.