If you kill a trigger enemy in the following method, it plays the "enemy death" sound. This is a good idea normally, but not if you are killing a trigger. Besides, you could always just use PlaySound.
npc trigger = Screen->LoadNPC(1);
if(trigger->HP != 0)
{
trigger->HP = 0;
}
I would suggest putting if(enemy_that_died != trigger) around the "play enemy death sound" code.
An example quest with this would be my iceblock quest, found in the script showcase forum.