How to make my enemy stop moving once dead?

I tried several ways, but it seems no matter what I try it doesn't work. He either sits still before he dies or the game object goes crazy and flys off screen.

 using UnityEngine;
 using System.Collections;
 using SpriteFactory;
 
 
  
 public class EnemyAi : MonoBehaviour {
     public Transform target;
     public int moveSpeed;
     public int rotationSpeed;
     public int maxDistance = 8;
     private Sprite sprite;
     public AudioClip swords;
     public int life = 100;
     public int points = 15;
     
     
  
     private Transform myTransform;
     
      IEnumerator Death() {
    yield return new WaitForSeconds(0.8f);
         
         Destroy(gameObject);
         PointCounter.points += points;
         
         
     }
  
     void Awake() {
        myTransform = transform;
        sprite = (Sprite)GetComponent(typeof(Sprite));
     }  
  
     
     void Start () {
        GameObject go = GameObject.FindGameObjectWithTag("Player");
  
        target = go.transform;
  
        maxDistance = 8;
 
     }   
  
     void FixedUpdate () {
        if(Vector3.Distance(target.position, myTransform.position) > maxDistance) {
  
          myTransform.position -= myTransform.right * moveSpeed * Time.deltaTime;{
              sprite.Play ("EnemyWalk");
                  if (life <=0) {
                     sprite.Stop ();
                 }
 }
 }
 }
     
     //Health and damage rate when enemy is hit
         void OnTriggerEnterSprite(SpriteCollider.CollisionData data) {
             sprite.Play("hurt");
                 if(sprite.IsAnimationPlaying ("hurt")){
                     audio.Play();{
                          life += -100;
                             if (life <= 0) {
                              
                                 sprite.Play ("death");
                                     StartCoroutine(Death());
                                     }
         
 }
 }
 }
 }