Before you begin following Tommy, look to your right to add an entry to your journal, then head up the hill a little to be given the honour of using Tommy's Weapon. Here you'll need to take out the enemies from a distance.
Tip: During this segment you'll have unlimited ammo on Tommy's weapon, so take a few minutes to get used to the bullet drop off.
Once you've taken out the three groups of enemies you'll return to Joel for a cutscene.
Head towards the music shop
After the cutscene has come to a close, jump on your horse and follow Joal. Eventually you'll have to get off your horse and continue through the building on foot, but before you do, climb over the red trailer on the left and collect the Trading Card 24/48 from the car in the water.
Head over to the entrance of the building and wait for Joel to lift up the collapsed roof, crawl through and open the door. Continue following Joel further into the building, then go into room 107 to find an Artefact 64/117 on the table, now head into the next room and take out the group of infected.
Once all the enemies have been taken out, wait for joal to open the door and continue through, slide through the gap on the left and a short scene will play out. When you regain control, sprint away to collect some supplies, then focus all your firepower on the Bloater to take it down.
Finally, follow the Joal a little more and then you'll view one last cutscene for this flashback.