NPC's dialouge. It's really simple, kinda. The player can walk up to peaceful NPC's and strike up a conversation. These NPC's are all survivors, most injured or trapped. Sometimes they'll have a useful bit of info, other times some spare supplies, and almost all of them have bits of lore and backstory to impart.
Now those aren't likely to be the final effects, those're pretty rough, but that is a promise. A promise that you, as a player, will be able to not only kill, but murder if that's your thing.
Designer of digital homocide simulators.