Help with a switch

Okay in my game the hero talks to a character by talking to the character the event starts the hero has to kill all monsters and return back to the character.... how do i get the even to end after i kill the monsters where do i place the switches?

it'd be easier done with a variable.
Every time one of the monsters is killed, add 1 to an empty variable.

when the time comes to check and see if all the monsters are dead, check to see if the variable is equal to the number of monsters they have to kill

edit: belongs in troubleshooting, not tutorials