Kill an ennemy open the way

Ok , so i watch a video , and i know a little how work event dispatchers. So i had done this : When an ennemy see the player he call an event “Alerted” , and when he die , he call again this event.
In the level BP have bind this event “Alerted” to an other event. So with a flip flop , when the ennemy see the player the doors rise , and when he die , the doors go down , but how do this when there is more than ennemy ?