object does not destroy

i made this script but the object is not destroyed when the hp = 0 or -. i dont know whats i did wrong and i hope tha you can help me.

here is my script :

var hitPoints = 100;
var bulletDamage = 100;

function OnCollisionEnter(coll:Collision){    
if(coll.gameObject.tag=="bullet")
{ hitPoints -= bulletDamage; }

if (hitPoints <=0){
  Destroy(gameObject);
  }
}

var hitPoints = 100;
var bulletDamage = 100;

function OnCollisionEnter(coll:Collision)
{    
   if(coll.gameObject.tag=="bullet")
   {
      hitPoints -= bulletDamage; 
      if (hitPoints <=0)
      {
         Destroy(gameObject);
      }
   }
}

it was right you just have to reaarange some stuff. a possibly more accurate method of doing it would be

function OnCollisionEnter(coll:Collision)
{    
   if(coll.gameObject.tag=="bullet")
   {
      hitPoints -= bulletDamage;
   }
}

function Update ()
{
   if (hitPoints <= 0)
   {
      Destroy(gameObject);
   }
}

try to keep your scripting neat and these kind of mistake will be easier for you to spot.