Multiplyaer FPS sprint speed does not work

I HAVE THIS WARNING: Assets/Scripts/FirstPersonController.cs(65,23): warning CS0219: The variable `speed' is assigned but its value is never used I FOLLOWED THE MIKE GEIG TUTORIAL ABOUT MERRY FRAGMAS AND BECAUSE OF THIS WARNING I CAN'T SPRINT. THE ANIMATION WORK'S, BUT MY SPEED DO NOT INCREASE. HERE IS THE SCRIPT:

using UnityEngine; using System.Collections;

[RequireComponent (typeof(CharacterController))] public class FirstPersonController : MonoBehaviour {

 public bool walkByDefault = true;
 public float runSpeed = 8.0f;
 public float movementSpeed = 5.0f;
 public float mouseSensitivity = 6.0f;
 public float upDownRange = 60.0f;
 public float jumpSpeed = 20f;
 float verticalVelocity = 0;
 CharacterController characterController;

 Animator anim;
 // Use this for initialization
 void Start () 
 {
     Screen.lockCursor = true;
     characterController = GetComponent<CharacterController> ();

 }
 
 // Update is called once per frame
 void Update () 
 {
     //Rotation

     float rotLeftRight = Input.GetAxis("Mouse X") * mouseSensitivity;
     transform.Rotate (0, rotLeftRight, 0);

     float rotUpDown = Input.GetAxis("Mouse Y") * mouseSensitivity;

     float currentUpDown = Camera.main.transform.rotation.eulerAngles.x;
     float desiredUpDown = currentUpDown - rotUpDown;


     //desiredUpDown = Mathf.Clamp (desiredUpDown, -upDownRange, upDownRange);

     Camera.main.transform.localRotation = Quaternion.Euler(desiredUpDown, 0, 0);

     //Movement
     float forwardSpeed = Input.GetAxis("Vertical") * movementSpeed;
     float sideSpeed = Input.GetAxis("Horizontal") * movementSpeed;

     verticalVelocity += Physics.gravity.y * Time.deltaTime;

     if ( characterController.isGrounded && Input.GetButtonDown ("Jump")) {
         verticalVelocity = jumpSpeed;
     }

     Vector3 speed = new Vector3 ( sideSpeed, verticalVelocity, forwardSpeed );

     speed = transform.rotation * speed;


     characterController.Move ( speed * Time.deltaTime);

     anim = GetComponentInChildren<Animator> ();
 }

 public void LateUpdate () {

     float speed = runSpeed;

 #if !MOBILE_INPUT
 
 // On standalone builds, walk/run speed is modified by a key press.
 // We select appropriate speed based on whether we're walking by default, and whether the walk/run toggle button is pressed:
     bool walkOrRun =  Input.GetKey(KeyCode.LeftShift);
     bool aim =Input.GetButton ("Fire2");

     if(aim)
         walkOrRun =false;

     speed = walkByDefault ? (walkOrRun ? runSpeed : movementSpeed) : (walkOrRun ? movementSpeed : runSpeed);
 // On mobile, it's controlled in analogue fashion by the v input value, and therefore needs no special handling.
     anim.SetBool ("Sprint" , walkOrRun);
     anim.SetBool ("Aim", aim);

 #endif
 }

}

ANY IDEAS?