The Door is set up such that it remains open so long as the alarm is not engaged. The moment the alarm is triggered, however, the doors are animated such that they slam shut and will not reopen until the alarm ends. It is important to note that Timelines are used to animate the doors. In fact, there are 2 separate Timelines - one to open the doors and another to close them. This allows the doors to open at one speed and close at another.
The door motion is actually triggered by receiving a signal from the Security Alarm Blueprint Interface, which is implemented by the camera, the door, and the alarm.
Also interesting about the door setup is that the door Timelines do not animate the doors directly. Instead, the Timelines each output a single float value, which is then used to interpolate between two vector locations - an "open" location and a "closed" location.