SourceTree silent installation is non-blocking - atlassian-sourcetree

Question

I am trying to install SourceTree on Windows non-interactively with my script.
I could find an option -s to install silently.
However, I kicked the SourceTreeSetup.exe with the option, it would return as soon as it run.
The setup process seems to be running on background.
I want to wait for the installation completed on my script, I couldn't find that way out.
I put a part of my powershell script here:
$url = "https://www.sourcetreeapp.com/"
$response = Invoke-WebRequest -Uri $url -UseBasicParsing
$downloadUrl = $response.Links | %{ $_.Href } | ?{ $_ -match "^.*/SourceTreeSetup-(\.?[0-9]+)+\.exe" } | Select-Object -First 1
$uri = New-Object System.Uri($downloadUrl)
$file = Split-Path $uri.AbsolutePath -Leaf
Write-Host "Downloading $file ..."
$ExePath = "$env:TEMP\$file"
if (Test-Path -Path "$ExePath")
{
Remove-Item -Path "$ExePath"
}
Invoke-WebRequest -Uri $downloadUrl -OutFile "$ExePath"
Write-Host "Installing..."
$process = Start-Process -FilePath "`"$ExePath`"" -ArgumentList #("-s") -Wait -PassThru
$exitCode = $process.ExitCode
if ($exitCode -eq 0 -or $exitCode -eq 3010)
{
Write-Host -Object "Installation successful"
Remove-Item "$ExePath"
Write-Host -Object "Cleaned up file: `"$ExePath`""
}
else
{
Write-Host -Object "Non zero exit code returned by the installation process : $exitCode."
}