Cannot Parent a Prefab Instantiated with Resource.Load()

Hello,

I instantiate a Prefab as follows:

 GameObject myBulletObj = Instantiate ((GameObject) Resources.Load("Prefabs/Bullets/AK47Bullet")) as GameObject;
             myBulletObj .transform.parent = this.transform;
             myBulletObj .name = this.name + " Bullet";
             myBulletObj .transform.localPosition = new Vector3 (0f, 0.7f, 0.9f);

But I get the following error:

Setting the parent of a transform which resides in a prefab is disabled to prevent data corruption

Why is this? Thanks!