...
else {
  _rotationX -= Input.GetAxis("Mouse Y") * sensitivityVert;
  _rotationX = Mathf.Clamp(_rotationX, minimumVert, maximumVert);
  float delta = Input.GetAxis("Mouse X") * sensitivityHor; 
  float rotationY = transform.localEulerAngles.y + delta;   
  transform.localEulerAngles = new Vector3(_rotationX, rotationY, 0);
}
...
