David had a good life above the sewers, with a good job and a nice wife, Erica. However, his mutant powers went out of control one day, and he accidentally erased his wife mind. Frightened of what had happened, he went to the Chicago Morlocks, and was soon their leader. He decided that before they went down into the sewers, they should each get one last "wish" to remember from above ground. He helped Shatter rescue his dog, Hank, from the pound, but became furious when Electric Eve killed her old pimp. He didn't want any of the Morlocks to be an accessory to murder. However, they soon came under attack by Sentinels. However, Litterbug's knowledge of the inner workings of the Sentinels helped the Morlocks "hijack" one, then let it take them back to it's base. Once there, the Morlocks (and Hank the dog) burst out of the robot, and used their combined powers to wreck havoc on the factory. After that, David hot wires a van, and he and the rest of the Morlocks drive as far south as they can go.
As the leader of the Morlocks, David is shown as being a kinder, gentler man who cares for the Morlocks like his family. However, Postman can also be violent in battle when someone threatens his group. He has a friendship of sorts with Litterbug, and he helped Litterbug burn off his old army tattoo with a piece of heated metal.
David can telepathically erase memories from someone, or wipe their mind entirely clean, as shown when he turns two policemen into vegetables.