When an aircraft in emergency initiates an immediate descent through controlled airspace (e.g., cabin depressurization), what action must the air traffic controller immediately take regarding other traffic in the area?

1. Broadcast an immediate emergency message to all aircraft in the vicinity ('ATTENTION ALL AIRCRAFT IN THE VICINITY OF... EMERGENCY DESCENT IN PROGRESS'), clear conflicting aircraft out of the emergency descent corridor, and inform adjacent ATC sectors.
2. Instruct the emergency aircraft to climb back up.
3. Shut down all radio frequencies immediately.
4. Wait until the aircraft lands before notifying other pilots.