Inside Job

First, James realised that such a technical glitch couldn't be done outside the control sector, it had to be done by someone who knew exactly how the cameras worked in order to disable those on that particular floor only without causing any problems. This kind of issue had to be taken care of by an expert and he suspected it had to be one in the security department.

If the videos were hacked then it would've made sense but then the police would be able to retrieve the video one way or the other and this went on to support what Bryan talked about. This killer was indeed very careful and skilful, almost making James compare him to the exorcist.

The more he thought about this the more convinced he was that it was an inside job. Someone in the hospital was working with the killer or was actually the killer. Who were they? The doctors? The nurses? The security? The possibility was endless and it served the make the case even harder to crack.