Oh that is easy. Everything is in your
bible
Create script area where ur last node point is. And name it for example "monsterdisappear".
Add this into ur OnStart
AddEntityCollideCallback("MyNameIsBob_1", "monsterdisappear", "makemedisappear", true, 1);
and separately:
void makemedisappear(string &in asParent, string &in asChild, int alState)
{
FadeEnemyToSmoke("MyNameIsBob_1, true/false); //true if u want to play sound effect and false if not.
SetEntityActive("MyNameIsBob_1, false); //Its up to you which one you use. Second one instantly deletes it. First one makes it go into smoke with effect ^^
}