how to let the 2 turrets at the back to not fire when the first turret in the front is still alive?

using UnityEngine;
using System.Collections;

public class turret : MonoBehaviour
{
public Rigidbody bullet;
public Transform bulletEmitter;
Transform player;
public bool shoot = false;
float shooting;
public float rateOfFire = 50f;
public int hp = 100;
public int score = 2;
[SerializeField]
GameObject particle;
Transform platform;
void Start()
{
print(hp);
particle.SetActive(false);
}

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

void Update()
{
    transform.LookAt(player);
    if (shoot && Time.time >shooting)
    {
        Shooting();
        shooting = Time.time + rateOfFire / 500;

    }
    if (hp <= 0)
    {
        transform.LookAt(platform);
        particle.SetActive(true);

    }
}

void OnTriggerEnter(Collider other)
{
    if (other.tag == "Player"&& hp>0)
    {
        Debug.Log("Range");
        shoot = true;
    }
    if(hp < 0)
    {
        transform.LookAt(platform);
        shoot = false;
        
    }
}
void OnTriggerExit(Collider other)
{
    if (other.tag == "Player")
    {
        shoot = false;
    }
}

void Shooting()
{
    Rigidbody bulletInstance;

    bulletInstance = Instantiate(bullet, bulletEmitter.position, bulletEmitter.rotation) as Rigidbody;

    bulletInstance.AddForce(bulletEmitter.forward * 1000);

}
void OnCollisionEnter(Collision col)
{
    if (col.gameObject.tag == "Bullet")
    {
        print("Health: " + hp);
        hp = hp - 20;
    }
}

}

Help please :frowning: