I would like to authenticate some of my user base against active directory and the rest by just using their umbraco password set in the back office. Is this possible?

I've installed the IdentityExtensions package and followed the documentation from here: https://our.umbraco.com/Documentation/Reference/Security/authenticate-with-AD (which is missing the mapper variable and did not compile initially without modification). I've got active directory sign on working but now my other users which are not in active directory will not pass authentication. Is there a way to have it check active directory first and then fall back on the built in umbraco authentication?