After speaking with Walter to start the mission, you will immediately be ambushed by a large group of Scabs. Help your buddy fend them off as you start on top of a glass roof overlooking the overpass, you have a little cover and a decent angle although, I would recommend hitting the wires on either side to keep mobile.

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Help Walter defend against the Scabs (left) and then chat with him near the chopper (right)

You’ll have to defend yourself for a minute whilst the Scabs continue to spawn and enter the area via the two off-ramps to the south. Once the minute is up, you just need to mop up any surviving enemies to continue. Afterwards drop down and speak with Walter for a scene.

Following the scene you’ll get a brief tutorial on Photo Booths, have a go at the Chaos Squad multiplayer mode if you want. When you are ready to continue, fast travel back to the Brewery and speak with Floyd to end the mission.