How to fire a bullet when the image target was detected in vuforia.

Please help, how to fire a bullet when image target are detected in vuforia

This is my bullet script.

public class Gun : MonoBehaviour {

public GameObject bulletPrefab;
public Transform spawnObject;
public AudioSource ShootAudioSource;
public Bounds bounds;

void Start() 
{
}

private void Update () 
{

	int numTouches = Input.touchCount;
	if (numTouches > 0) {
		for (int x = 0; x < numTouches; x++) {
			Touch touch = Input.GetTouch (x);
			if (touch.phase == TouchPhase.Began) {
				spawnSphere ();
			}
		}
	} else if (Input.GetMouseButtonDown (0)) { // mouse clicked somewhere in unity editor
		spawnSphere ();
		ShootAudioSource.Play ();
	}

	bounds.center = transform.position;

}

public void spawnSphere() 
{
	// create object and give it force depending on image tracker on gon position/rotation
	// create game object @ position/rotation of gun
	GameObject go = Instantiate (bulletPrefab, spawnObject.position, spawnObject.rotation) as GameObject;
	go.GetComponent<Rigidbody> ().AddForce (transform.forward * 30, ForceMode.VelocityChange);

}

}

Can anyone help? Thank you.

@ryzasamson
You need to Instantiate your bullet prefab in OnTrackingFound Method which you can find in DefaultTrackableEventHandler Script under ImageTarget Object.Hope this helps.