DownloadCompleteEvent fires twice - vb.net

Question

I have a windows form which lets the user select a file name and download it, Once the download is complete, a download finished event is triggered which unzips the downloaded file and processes it further.
The downloadComplete event seems to be triggered twice which is causing the unzipping action to happen twice. Is there a reason why the event would be fired twice?
below is the function which triggers the download and Handles the download complete event.
Private Async Sub Btn_download_Click(sender As Object, e As EventArgs) Handles Btn_download.Click
Dim fileNameRows As DataGridViewSelectedRowCollection = datagridview_cloudContent.SelectedRows
Dim fileName As String
Dim fileType As String = AWSGlobals.CONTENT
For Each fileNameRow As DataGridViewRow In fileNameRows
fileName = fileNameRow.Cells(0).Value.ToString() & ".zip"
Try
Await DownloadAsyncFile(fileName, fileType)
Catch ex As Exception
CSMessageBox.ShowError("Content Import failed : ", ex)
End Try
Next
End Sub
Private Function UnzipAndImport(filename As String) Handles s3obj.DownloadDone
If Not System.IO.Directory.Exists(AWSGlobals.ContentPath & Path.GetFileNameWithoutExtension(filename)) Then
Dim zipFilePath As String = DiskPath & filename
Dim zipFileArchive As ZipArchive = ZipFile.OpenRead(zipFilePath)
Dim FullPathOfContent As String = DiskPath
ExtractToDirectoryOverWrite(zipFileArchive, FullPathOfContent, True)
ImportExport.BatchImportContent(New ArrayList(New String() {ExtractedPath}), objmanager)
End If
End Function
In the class that handles the downloads, the download method is implemented as below :
Public Function DownloadAsyncFile(FileName As String, FileType As String)
Try
Dim Address As String
AddHandler fileReader.DownloadFileCompleted, Sub(sender, e) download_complete(FileName)
AddHandler fileReader.DownloadProgressChanged, AddressOf Download_ProgressChanged
fileReader.DownloadFileAsync(New Uri(Address), AWSGlobals.ContentPath + FileName)
Catch ex As Exception
MsgBox( ex.Message)
End Try
End If
End Function
Private Sub download_complete(filename As String)
RaiseEvent DownloadDone(filename)
End Sub
Can someone tell me if this implementation causes the download complete event to fire twice when just one file is being downloaded?