— William Friedkin
Killer Joe is a movie haunted by television sets, right from the opening scene, where a television is on in the middle of the night, for no apparent reason, eerily showing static noise, while everyone's asleep.
When Ansel arrives in the living room, after having been woken up by Chris, the first thing he does is change the channel, and we're treated to a curious bit of foreshadowing, as the television shows us the scene we're missing at the end of the film.
But for the most part, TVs in Killer Joe exist as a perpetual source of distraction and annoyance, and Friedkin makes a ritual of people turning them off. It starts with Joe turning off a TV upon arriving at the Smiths' trailer for the first time, because the TV is too loud, and Dottie can't hear him otherwise.
Joe has to turn off the same TV, again, after Ansel forgets to do so before leaving the room.
And finally, because the damn thing just doesn't seem to go away, and effectively setting the tone for the final scene of the film, Joe deals with it in a more... definitive manner.