GetButtonDown problem | C#

Hello, I'm trying to make a weapon script that allows me to change the firing mode from being able to hold down the trigger on a machine gun, or make it so you have to keep clicking for the gun to keep firing, like on a pistol.

There is one problem tho, when the script uses GetButtonDown, it no longer works.

 using UnityEngine;
 using System.Collections;
 
 public class thePlayerShoot : MonoBehaviour {
 
 
     private bool cooling = false;
     public float cooldown = 0.7f;
     private float maxcooldown;
     public AudioClip gunshot;
     public AudioClip gunhit;
     public string checkTag = "enemy";
     public GameObject blood;
     public GameObject effect1;
     public GameObject effect2;
     public int gunPower = 5;
     public int dist = 70;
     public GameObject theCamera;
     public GameObject gunBarrel;
 
 
     private int oldGunPower;
 
     public GameObject gun;
     private bool special = false;
     private float specialTime = 15;
     public Material defaultMat;
     public Material specialMat1;
     public GameObject specialEffect;
     public AudioClip instaKill;
 
     public int health = 3;
     public GameObject explosion;
     public AudioClip explosionaudio;
 
     public bool canHoldTrigger = true;
 
 
     
     void Start () {
         maxcooldown = cooldown;
         oldGunPower = gunPower;
     }
 
     void Update () {
 
                 if (Time.timeScale == 0)
                         return;
 
 
                 if (health <= 0)
                         Application.LoadLevel ("holdTheLine");
 
                 if (special == true) {
                         specialTime -= Time.deltaTime;
                         gun.gameObject.renderer.material = specialMat1;
                         gunPower = 100;
                 }
 
                 if (specialTime <= 0) {
                         gun.gameObject.renderer.material = defaultMat;
                         special = false;
                         specialTime = 15;
                         gunPower = oldGunPower;
                 }
 
 
                 if (cooling == true) {
                         cooldown -= Time.deltaTime;
                 }
 
                 if (cooldown < 0) {
                         cooling = false;
                         cooldown = maxcooldown;
                 }
 
 
 
 
 
 
 
         if (canHoldTrigger == true)
                 if (Input.GetButton ("Fire1"))
                     Shoot();
             
 
         if(canHoldTrigger == false)
             if (Input.GetButtonDown ("Fire1"))
                 Shoot();
 
 }
 
 
 
 
 
 
 
     public void Shoot(){
 
         RaycastHit hit = new RaycastHit ();
         bool foundHit = false;
 
 
         foundHit = Physics.Raycast (transform.position, transform.forward, out hit, dist);
         if (cooling == false) {
             audio.PlayOneShot (gunshot, 0.4F);
             Instantiate (effect1, gunBarrel.gameObject.transform.position, effect1.transform.rotation);
             Instantiate (effect2, gunBarrel.gameObject.transform.position, theCamera.transform.rotation);
             cooling = true;    
             if (foundHit) {
                 if (hit.transform.tag == checkTag) {
                     print ("Hit an enemy!");
                     audio.PlayOneShot (gunhit, 0.6F);
                     Instantiate (blood, hit.transform.position, blood.transform.rotation);
                     theEnemy enemyScript = hit.transform.GetComponent<theEnemy> ();
                     enemyScript.health -= gunPower;
                 } else { 
                     if (hit.transform.tag == "dontshoot") {
                         audio.PlayOneShot (gunhit, 0.6F);
                         audio.PlayOneShot (explosionaudio, 0.7F);
                         health -= 1;
                         hit.transform.gameObject.AddComponent<Rigidbody> ();
                         hit.rigidbody.AddForce (0, 1000, 0);
                         hit.rigidbody.AddForce (0, 1000, 0);
                         Instantiate (explosion, hit.transform.position, explosion.transform.rotation);
                         Instantiate (explosion, hit.transform.position, explosion.transform.rotation);
                         Destroy (hit.transform.gameObject, 3);
                     } else {
                         if (hit.transform.tag == "special") {
                             special = true;
                             audio.PlayOneShot (gunhit, 0.6F);
                             audio.PlayOneShot (instaKill, 2);
                             Instantiate (specialEffect, hit.transform.position, specialEffect.transform.rotation);
                             Destroy (hit.transform.gameObject);
                         }
                         
                         
                         if (hit.transform.tag == "pushable") {
                             hit.rigidbody.AddForceAtPosition (10 * gun.transform.forward, hit.point);
                             audio.PlayOneShot (gunhit, 0.6F);
                         }
                     }
                 }
             }
         }
     }
 
 
 
 }

There are no errors in the console.

Any help would be greatly appreciated, thanks!