Destroy enemy using raycasts

Hi all, this script is attached to an invisible cube at the end of my gun it fires raycasts and if it hits anything in the scene it spawns a particle effect of sparks. If the rays collide with something with a tag of "Enemy" then it spawns a blood particle effect, this all works how it should apart from the ApplyDamage part which is supposed to destroy the enemy if its health goes to zero. This dosent work as my Enemy dosent have health and dosent know when to die, this is what I think anyway. Is my Enemy supposed to have a damage receiver sort of script which tells it when to destroy itself, I need some help with this can anyone lend a hand?

script

 var amountOfShots = 30;

var reloadTime = 1.5;

var refireRate : float = 0.1;

function ShotPoller()

{

while(true)

{

 if(Input.GetButton("Fire1"))

 {

     Shoot();

     

     yield WaitForSeconds(refireRate);

 }

 if(Input.GetKeyDown("r")){

     Reload();

 }



 yield;

}

}

function Start()

{

StartCoroutine(ShotPoller());

}

if(Input.GetKeyDown("r")){

Reload();

}

function Reload (){

yield WaitForSeconds(reloadTime);

amountOfShots = 30;

}

var shotSound : AudioClip;

var bloodPrefab : Transform;

var sparksPrefab : Transform;

var hit : RaycastHit;

var range = 500;

function Shoot (){

 if(amountOfShots > 0){

     amountOfShots--;

     if(shotSound){

     audio.PlayOneShot(shotSound);

 }

if (shotSound) audio.PlayOneShot(shotSound);

var hit: RaycastHit;

if (Physics.Raycast(transform.position, transform.forward, hit)){

 var rot = Quaternion.FromToRotation(Vector3.up, hit.normal);



 if (hit.transform.tag == "Enemy"){ 



     if (bloodPrefab) Instantiate(bloodPrefab, hit.point, rot); 



     hit.transform.SendMessage("ApplyDamage", 20, SendMessageOptions.DontRequireReceiver); 



 } else { 



     if (sparksPrefab) Instantiate(sparksPrefab, hit.point, rot);



 }

}

}

}