On Death:

thingid
count (optional)




This will cause a trigger to not activate until all things of thingid are killed or are no longer on the map.

The optional count is a numerical value which causes a counter based on how many thingid are left to kill. The values should be greatest to lowest as you read down your script, if used/

ex.
start_map map01
radiustrigger 0 0 -1
ondeath zombieman 2
tip "two to go!"
end_radiustrigger

radiustrigger 0 0 -1
ondeath zombieman 1
tip "one to go!"
end_radiustrigger
end_map
This can be used to make an event wait until a single item is picked up, or until a group of monsters are killed before allowing this trigger to execute.