Chuck will have to have a long conversation with Andy about the collective intelligence of the zombies that Andy has killed. Thankfully, they will have this talk on top of a group of slot machines, so no zombies can get them.
If Chuck leaves Andy's presence after initiating the conversation but before Andy joins, Andy will defect, saying "It's too much." or "The only way out is the easy way out." He will commit suicide by putting his shotgun to his chin, and blowing his own brains out.
While Andy's suicide is unlikely to happen in single-player, it is common in co-op, as another player being too far away from Andy will automatically trigger the death. Thus, both players must be present when talking Andy out of his suicide attempt.
During the introduction there is an unnamed survivor, with the same character model as Andy, that can be seen being attacked by a zombie as the infected spectator kills a man.