3D Top Down Rotation (PLZ HELP)

So I’m making a 3D top down Shooting game and it coming out ok but I just can’t get the aim to rotation right. Here my code, what am I’m doing wrong.

var mouse : Vector3;
var rot : Quaternion;

function Update () 
{
mouse = Camera.main.ScreenToWorldPoint(Input.mousePosition);
rot = Quaternion.LookRotation(target.position - mouse, Vector3.forward);
transform.LookAt(rot);
}

PLZ HELP

mouse = Camera.main.ScreenToWorldPoint(Input.mousePosition);
rot = Quaternion.LookRotation(transform.position - mouse, Vector3.forward);
transform.rotation = rot;
transform.eulerAngles = new Vector3 (0, 0, transform.eulerAngles.z);
//rigidBody2D.angularVelocity = 0; //if needed