Pull down refresh indicator not stopping after complete loading

Here is my sample xaml

<ListView ItemsSource="{Binding EmployeeList}" HasUnevenRows="True" 
                          IsPullToRefreshEnabled="True" RefreshCommand="{Binding RefreshCommand}" IsRefreshing="{Binding IsBusy}">
                    <ListView.ItemTemplate>
                        <DataTemplate>
                            <ViewCell>
                                <StackLayout>
                                    <Label Text="{Binding Name}" TextColor="Black"/>
                                    <Label Text="{Binding Department}" TextColor="Black"/>
                                </StackLayout>
                            </ViewCell>
                        </DataTemplate>
                    </ListView.ItemTemplate>
                </ListView>
            </StackLayout>
            <Image Source="{Binding GetSource}"/>

i want that when a user pull down on list view then it will load a image from URI(just playing around)

here is my view model

    public class MainViewModel : INotifyPropertyChanged
    {
        private List<Employee> _employeeList { get; set; }

        private string _source { get; set; }

        public string GetSource { get { return _source; } set { _source = value; OnPropertyChanged(); } }


        Command _refreshCommand;
        public Command RefreshCommand
        {
            get
            {
                return _refreshCommand;
            }
        }

        public List<Employee> EmployeeList
        {
            get { return _employeeList; }
            set { _employeeList = value;
                OnPropertyChanged();
            }
        }

        // class constractor
        public MainViewModel()
        {
            var employeeServices = new EmployeeServices();
            EmployeeList = employeeServices.GetEmployees();
            _refreshCommand = new Command(ShowImage);
        }

        private void ShowImage()
        {
            var imagesou = "https://www.hindustantimes.com/rf/image_size_640x362/HT/p2/2016/04/08/Pictures/_e76dfb4e-fd62-11e5-bced-6695953481e2.jpg";
            GetSource = imagesou;
        }

        #region PropertyChange
        public event PropertyChangedEventHandler PropertyChanged;

        protected virtual void OnPropertyChanged([CallerMemberName] string propertyName=null)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }
        #endregion
}

Problem is that when I pull down for refreshing,then it works fine,but after complete image loading the refresh indicator is not stopping,so how to do this?