coop_mission_haunted: Stuck in room with 4 skulls and a pillar

Just tried playing this map today via the Steam Workshop. When I first spawn, there's a small obelisk in the middle of the room with 4 glowing green skulls with a faint pillar of light that rises to the top of the room.

There are 4 doors that are wide open that lead to the outer courtyard, presumably.

When approaching those doors, they close automatically and will not open until I reach a far away distance.

How can I get out of this room? No enemies have spawned yet and there seems to be no way to trigger enemy spawns or anything else of the sort.