I would consider the Killers pop music, not indie.

Musically, the two genres are extremely different. Emo uses a lot of kind of hard rock guitar riffs except you can barely hear it because the singer is usually screeching/screaming..not singing. Other emo, like Dashboard Confessional is strictly acoustic.

Indie gets its roots more from alternative/grunge/prog rock. Really modern indie bands use more and more of an electronic sound.