Close browser tab created using shell.openExternal


I am creating a browser tab using shell.openExternal(localhost:3000/mySite)
Is it possible to programmatically close this tab from either electron or the localhost:3000/mySite context?

It seems to me like this cannot be done from within electron.
Additionally - javascript methods like window.close() only seem to work if the window was opened using (which is not the case here).