Need help to loop an array of respawn prefabs after shooting them.

I'm trying to make a FPS scene with 5 targets in front of player spawning randomly at specific locations. I want to shoot the target and when I hit the target the next one will show up. This script is attached to my prefab Target.

public class pomperHit : MonoBehaviour {

 Rigidbody rb;
 Vector3 origLoc;
 Quaternion origRot;
 private TargetSpawner targetSpawner;

 void Start()
 {
     rb = GetComponent<Rigidbody> ();
     origLoc = transform.position;
     origRot = transform.rotation;
     targetSpawner = GetComponent<TargetSpawner> ();
 }
 void Update ()
 {
     if (Input.GetKeyDown ("r"))
     {
         transform.position = origLoc;
         transform.rotation = origRot;
     }
 }
 void OnCollisionEnter (Collision col)
     {
     if (col.gameObject.tag  == "Bullet")
         {
         rb.AddRelativeForce(Vector3.forward  * -250f);
         targetSpawner.SpawnRoutine ();
         Destroy (col.gameObject);
         }
     }

}

and this script attached to my spawner

using System.Collections; using System.Collections.Generic; using UnityEngine;

public class TargetSpawner : MonoBehaviour {

 public Transform[] spawnLocations;
 public GameObject[] spawnPrefab;
 public GameObject[] spawnClone;


 void Start()
 {
     SpawnRoutine ();
 }
 public void SpawnRoutine()
 {        
     int i = Random.Range (0, 5);
     spawnClone [i] = Instantiate (spawnPrefab [i], spawnLocations [i].transform.position, Quaternion.Euler (0, 87f, 0)) as GameObject;                
 }        

}