By default, this room is locked down and the door cannot be opened or destroyed. Agents can open the door as a possible reward for Data Hub hacking. Something to the effect of "Armory blast doors disengaged" would show up as a message for when this hack is achieved.
Afterwards, the doors open and inside is a terminal. Interacting with this terminal will begin a siege, where the terminal must be defended in this time. If the terminal is destroyed before the siege ends, the armory's items remain locked and cannot be retrieved by any means. The security mech will also be permanently rogue.
However, if the terminal is successfully defended, the station's Armory is the survivors' to pillage. It would spawn a collection of items
-1 random pick up item for every 4 players in the lobby
-a resupply point
-a few medkits