Set up a new Alexandria on normal.

You probably need 2 people to do this. There will be a sequence of 4 switches, each one on a building, each checkpoint you will go to a building.

Go to the side of the building and you'll see a switch, hit the switch, go to the next building, hit the switch and so on...

Then you'll come up on the club, go inside, but don't kill anybody and you'll see Bruts and Grunts dancing.