Unity3D Ai wont shoot

So my AI enemy wont shoot at the player some of the time, some of my enemy prefabs wont shoot at the player they just look at it. I've tried a whole bunch of things but nothing has worked. Please help, if you get this AI working your name will go into my game credits.

My AI script (contains shooting and walking)

 var distance;
 var target : Transform;    
 var lookAtDistance = 15.0;
 var stopDistance = 3;
 var moveSpeed = 5.0;
 var damping = 6.0;
 
 var damage:float = 17;
 var range = 100.0;
 var force = 10.0;
 var muzzleFlash : Renderer;
 var muzzleLight : Light;
 
 
 var Health = 100;
 var deadReplacement : Transform;
 var dieSound : AudioClip;
 
 static var isDead = false;
 
 static var allowfire : boolean = true;
 
 function Start (){
 muzzleFlash.enabled = false;
 muzzleLight.enabled = false;
 allowfire = true;
 }
 
 function Update () {
     target = GameObject.FindWithTag("Player").transform;
     distance = Vector3.Distance(target.position, transform.position);
  
     if((distance < lookAtDistance)){
     lookAt ();
     }
     if(allowfire == true){
     fire();
 }
 }
 
  
 function lookAt (){
     var rotation = Quaternion.LookRotation(target.position - transform.position);
     transform.rotation = Quaternion.Slerp(transform.rotation, rotation, Time.deltaTime * damping);
     transform.Translate(Vector3.forward * moveSpeed *Time.deltaTime);
     animation.Play("walk");
 }
 
 function ApplyDammage (TheDammage : int)
 {
     Health -= TheDammage;
     
     if(Health <= 0)
     {
         Dead();
     }
 }
 
 function Dead () {
     // Destroy ourselves
     Destroy(gameObject);
     Destroy(transform.parent.gameObject);
     
     // Play a dying audio clip
     if (dieSound)
     AudioSource.PlayClipAtPoint(dieSound, transform.position);
 }
 
 static function CopyTransformsRecurse (src : Transform,  dst : Transform) {
     dst.position = src.position;
     dst.rotation = src.rotation;
     
     for (var child : Transform in dst) {
         // Match the transform with the same name
         var curSrc = src.Find(child.name);
         if (curSrc)
             CopyTransformsRecurse(curSrc, child);
     }
 }
 
 function fire(){
 allowfire = false;
 audio.Play();
         
 var direction = transform.TransformDirection(Vector3.forward);
 var hit : RaycastHit;
  
 // Did we hit anything?
 if (Physics.Raycast (transform.position, direction, hit, range)) {
 Debug.DrawRay(transform.position, direction * range, Color.green);
 // Apply a force to the rigidbody we hit
 if (hit.rigidbody)
 hit.rigidbody.AddForceAtPosition(force * direction, hit.point);
 hit.collider.SendMessageUpwards("ApplyDamage", damage, SendMessageOptions.DontRequireReceiver);
 }
 
 muzzleFlash.renderer.enabled = true;
 muzzleLight.enabled = true;
 yield WaitForSeconds (0.04);
 muzzleFlash.renderer.enabled = false;
 muzzleLight.enabled = false;
 
 
 yield WaitForSeconds(0.3);
 allowfire = true;
 }
 
 function OnTriggerEnter(hit:Collider){
 if(hit.tag == "Player"){
 hit.transform.SendMessage("Damage",damage);
 }
 }