3rd pserson shooter camera issue

I am developing a third person shooter game for mobiles. Here I am using the following script to control the camera movement.

using UnityEngine; using System.Collections;

public class mouse_controller : MonoBehaviour {

 [AddComponentMenu("Camera/Simple Smooth Mouse Look ")]

 Vector2 _mouseAbsolute;
 
 Vector2 _smoothMouse;
 
 public Vector2 clampInDegrees = new Vector2(80, 20);
 
 public bool lockCursor;
 
 public Vector2 sensitivity = new Vector2(0.9, 0.9);
 
 public Vector2 smoothing = new Vector2(2, 2);
 
 public Vector2 targetDirection;
 
 public Transform target;

 public float range = 1000;
 public float force = 1000;

 // Use this for initialization
 void Start () 
 {
     targetDirection = transform.localRotation.eulerAngles;
 }
 
 // Update is called once per frame
 void Update () 
 {
     transform.position = new Vector3 (target.position.x,target.position.y,target.position.z);


     
         if(Input.mousePosition.x > Screen.width/1.5f && Input.mousePosition.y < Screen.height/3)
         {
             
         }
         else
         {
             if (Input.touchCount == 1 && Input.GetTouch (0).phase == TouchPhase.Moved) 
             {
                 Screen.lockCursor = lockCursor;
                 var targetOrientation = Quaternion.Euler(targetDirection);
                 
                 var mouseDelta = new Vector2(Input.GetAxisRaw("Mouse X"), Input.GetAxisRaw("Mouse Y"));
                 mouseDelta = Vector2.Scale(mouseDelta, new Vector2(sensitivity.x * smoothing.x, sensitivity.y * smoothing.y));
                 
                 _smoothMouse.x = Mathf.Lerp(_smoothMouse.x, mouseDelta.x, 1f / smoothing.x);
                 _smoothMouse.y = Mathf.Lerp(_smoothMouse.y, mouseDelta.y, 1f / smoothing.y);
                 _mouseAbsolute += _smoothMouse;
                 
                 //--- Horizontal Movement ---
                 if (clampInDegrees.x < 85)
                 {
                     _mouseAbsolute.x = Mathf.Clamp(_mouseAbsolute.x, -clampInDegrees.x * 0.5f, clampInDegrees.x * 0.5f);
                 }

                 var xRotation = Quaternion.AngleAxis(-_mouseAbsolute.y, targetOrientation * Vector3.right);
                 transform.localRotation = xRotation;
                 
                 //--- Vertical movement ---
                 if (clampInDegrees.y < 25)
                 {
                     _mouseAbsolute.y = Mathf.Clamp(_mouseAbsolute.y, -clampInDegrees.y * 0.5f, clampInDegrees.y * 0.5f);
                 }
                 transform.localRotation *= targetOrientation;
                 
                 var yRotation = Quaternion.AngleAxis(_mouseAbsolute.x, transform.InverseTransformDirection(Vector3.up));
                 transform.localRotation *= yRotation;
             }
         }
 }

}

When i drag on the screen camera smoothly rotate. But the issue is when click after the fire button(for shoot)with right hand,same time user also has the provision to change the camera position with his left hand. After pressing the fire button camera suddenly switch to the left touched position without considering the Lerp values. This will happen rarely. please help me to findout the issue

I expect an output like Frontline Commando2

Thanks in advance..