Pure hypothetical here

Lets say that two employees in a private chat say something about wanting to hurt their boss because he is a terrible person. So the boss tricks one of the employees into giving their password up to look at a specific piece of work related material (stupid I know) and then proceeds to go beyond the work related material and look into the chat. Boss goes to HR with the chat saying they feel "threatened" and both of the employees are fired. I feel like the boss could be liable in a civil suit for violation of privacy because the password was given to view very specific material unrelated to the chat. thoughts?