I'm creating an FPS game and I can't work out how to loop the shoot animation of the enemy I've attached the script to until my player dies

The script below is attached to the enemy on my game.

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

public class EnemyMovement : MonoBehaviour {

    private Animator attack;

    Transform player;

    UnityEngine.AI.NavMeshAgent nav;



    void Awake()
    {
        player = GameObject.FindGameObjectWithTag("Player").transform;

            nav = GetComponent<UnityEngine.AI.NavMeshAgent> ();

    }

The code just below is getting the enemy to stop at a certain distance and shoot from the trigger "Attack". (Below and above are all the same code).

    // Update is called once per frame
    void Update () {


        nav.SetDestination(player.position);
        float distance = Vector3.Distance(this.transform.position, player.position);
        if (distance < 10f)
        {


            Animator an = GetComponent<Animator>();
                an.SetTrigger("Attack");

        }


        Debug.Log("distance" + distance);


    }

}

This script basically uses the Nav Agent to make the enemy go towards my player and to start a shoot animation when the enemy is at a certain range.

Any help would be great. Thank you.