The DJ is a character that helps out the survivors by broadcasting his messages and speeches through the radio. He is the one that tells the survivors to head to the shelters.
The DJ was found near the end of the Stonewood questline. He was broadcasting from Plankerton to give the survivors some moral support on not giving up.The Commander and Ray heard his broadcast and decided to head to Plankerton to help them. When the Commander set up the Storm Shield in Plankerton, the DJ was in need of immediate rescue as the storm got worst in his location. Because of that urgent emergency, Ray sent Pop out to find him. As the storm got darker, Ray told Pop to come back, but he refused and continued his search for the DJ. Pop found him but was in trouble, the robot distracts the Husks to get the DJ out of there, thus leading to evil Pop for a while. Eventually, they did found him and rescued him (No thanks to evil Pop). When rescued, he asked the Commander if he/she can get him his broadcasting equipment to continue his moral support to the survivors of Plankerton. Now safe and reassuring the survivors out there. He broadcasts his messages to tell all survivors to head to the Shelters that Ray has built for them.