It's good that your brother took my advice yesterday and moved all the remaining funds to a new address. and I'm sorry for what he is going through right now. Just try and make him stronger.
For the aspect of reporting this issue to the authorities, I think you guys can start by reporting the scammers Twitter profile first to Twitter and dropping a warning message in their tweet comment section so that other users can be aware and take precautions to not fall victim to such attacks.
 
A verified Twitter page does not make it entirely legit; even the real Twitter owner can use the account for scams. Talk more about the fact that people can now buy the blue badge by just paying a few dollars, and Elon and his team will grant them that badge. Again, sorry for your brother's health, and I wish him a quick bounce back.