How do you make an event happen when a Boss is killed?

[BURROW]

Im making a KOTH map right now, that spawns the HHH after a team caps, I want to make it so the point is locked until the boss is killed, I have the system for locking but how would you make the CP unlock? How do I detected when the boss is killed? Any help or ideas is appreciated.

 

[Box Of Paper]

To detect HHH's death:
- Place a "trigger_multiple" that covers the whole map (or just where HHH can move)
- Tick the "Everything" flag of the trigger
- Setup a "filter_activator_class" for the "headless_hatman" class
- Set the trigger_multiple's filter to the above filter_activator_class
- Use the trigger_multiple's OnEndTouch to fire an Output whenever HHH dies

This method dirts the map a bit since you need to place a trigger around a wide area, if you don't mind a small delay after the death then there's a better solution, check this other post:
https://tf2maps.net/threads/making-the-hhh-only-spawn-once.48089/#post-496041