Ending: Did [blank] really shoot [blank], or did [he/she] actually shoot [blank] (SPOILERS!)
At the end when Jonah popped out with the rifle and aimed it at Mel, the screen goes black at the end and about 2 seconds later you hear the single gunshot. Assumption is that he shot Mel.
However, I think the writers wanted to leave some ambiguity there. Jonah probably knows that Ruth is dead (or being hunted), and he thought very highly of her. Mel is sitting there holding the lamb jar talking about what's in it, so that's a good indication that may be dead, and Jonah had the jar so probably knew what was in it. He may have blamed his mother, and rightfully so. Remember, he was at the point where he was ready to leave town to go live with grandpa, but Wendy somehow convinced him to stick around. Did Jonah shoot Wendy and not Mel??