How to invoke the command for groupbar item in WPF GroupBar control?

<syncfusion:GroupBar ItemsSource="{Binding  GroupItemCollection}" VisualMode="StackMode">
  <syncfusion:GroupBar.ItemContainerStyle>
    <Style TargetType="{x:Type syncfusion:GroupBarItem}" >
      <Setter Property="Header" Value="{Binding Header}"/>
      <Setter Property="Content" Value="{Binding Content}"/>
      <Setter Property="IsSelected" Value="{Binding IsSelected}" />
    </Style>
  </syncfusion:GroupBar.ItemContainerStyle>
  <i:Interaction.Triggers>
    <i:EventTrigger EventName="MouseDown">
      <command:EventToCommand Command="{Binding MouseDownClick}"
          CommandParameter="{Binding InvokeParameter}" PassEventArgsToCommand="True"/>
    </i:EventTrigger>
  </i:Interaction.Triggers>
</syncfusion:GroupBar>

public class ViewModel
{
  private ICommand mouseDownClick;
  public ICommand MouseDownClick
  {
     get { return mouseDownClick; }
     set { mouseDownClick = value; }
  }
 
  private ObservableCollection<Model> groupItemCollection;
  public ObservableCollection<Model> GroupItemCollection
  {
     get { return groupItemCollection; }
     set { groupItemCollection = value; }
  }
 
  public ViewModel()
  {
     GroupItemCollection = new ObservableCollection<Model>();
     GroupItemCollection.Add(new Model() { Header = "GroupBarItem1", Content = "This is GroupBarItem", IsSelected = true });
     GroupItemCollection.Add(new Model() { Header = "GroupBarItem2", Content = "This is GroupBarItem1", IsSelected = true });
     GroupItemCollection.Add(new Model() { Header = "GroupBarItem3", Content = "This is GroupBarItem2", IsSelected = false });
     GroupItemCollection.Add(new Model() { Header = "GroupBarItem4", Content = "This is GroupBarItem3", IsSelected = true });
     GroupItemCollection.Add(new Model() { Header = "GroupBarItem5", Content = "This is GroupBarItem4", IsSelected = true });
     MouseDownClick = new DelegateCommand<object>(MouseDownClicked);
  }
 
  private void MouseDownClicked(object obj)
  {
     MessageBox.Show("Mouse down event called ");
  }
}

public class Model : NotificationObject
{
 private string header;
 public string Header
 {
   get { return header; }
   set { header = value; }
 }
 
 private string content;
 public string Content
 {
   get { return content; }
   set { content = value; }
 }
 
 private bool isselected;
 
 public bool IsSelected
 {
   get { return isselected; }
   set { isselected = value; }
 }
 
 private int invokeParameter = 1;
 
 public int InvokeParameter
 {
   get { return invokeParameter; }
   set { invokeParameter = value; RaisePropertyChanged("InvokeParameter"); }
 }
}