why does my enemy instant spawn bullets

so i have a script and it looks like this:

 var target : Transform; // The player
 var safeDistance = 10; //How close the player can be
 var Bullet : Rigidbody;
 var Barrel : Transform;
 var ShootDelay = 2;
  
 function Update(){
  
 //check how close the player is
 var distanceToPlayer = Vector3.Distance(this.transform.position, target.transform.position);
  
 // checks if player is still in safeDistance or otherwise it will call shoot function
 if(distanceToPlayer <= safeDistance){
         Shoot();
 }
 }
  
 //this is the shoot function
  
 function Shoot(){
         var rocketInstance : Rigidbody;
         rocketInstance = Instantiate(Bullet, Barrel.position, Barrel.rotation);
         rocketInstance.AddForce(Barrel.forward * 5000); 
         yield WaitForSeconds(ShootDelay);
 // needs to wait for ShootDelay seconds and then do it again
 }

but why is my enemy not waiting 2sec before firing again.

thanks for helping me