As the factory is isolated from outside communication, and as a result the sibyl network, the staff at the factory have only themselves to entertain them. More to the point, they have Yuuji. He is bullied and tormented, and his treatment is condoned by the factory management as they feel that this is a natural component of a healthy social heirarchy and that this behaviour is to be expected and is neccessary to keep people's stress levels down, a key factor in maintaining healthy psycho-passes, which otherwise cannot be measured.
This proves to be short-sighted as Yuuji develops a very troubled mindset under this torment, and being unable to leave due to the Sibyl System's judgement about his profession, slowly becomes prey to madness.
He is mysteriously provided a program to alter the drones the factory is building into temporary tools to use in any way he wishes. Yuuji promptly takes the opportunity to murder three of his tormentors. This causes the MWPSB to investigate, and when Kogami makes the connection that he has the most likely motive, he provokes him by making him believe he will be arrested soon.
Unable to stomach the thought of Kogami making his crimes known and him being put into isolation as a criminal(or killed), Yuuji uses the program to control the drones again, falling for the trap and proving his guilt. However, before he can be arrested he almost manages to kill Kogami and Akane before being subdued and his drones stopped.