Back to Reality

Set up the barricades in the marked location and wait for the horde of undead to swarm. Defend yourselves and take them all out. Once done, grab some of the food and drinks around to recover your hp. Talk to Trevor again and you'll receive a flare gun. Head outside the village and aim for the explosive barrels on the bridge. Take note that the flare gun has very limited range. You may need to kill a few zombies to get near or you can climb the wooden ledge using the ladder on the right side of the bridge. Once the bridge has been taken out, the quest will be complete.