Continuity mistake: [Blu-ray] When Garth runs back downstairs to the kitchen, where Mandy was asleep, she is just waking up when he comes back in. As he enters the room, she is resting her left elbow on the table, using her left hand to smooth her hair and her right hand is covering her nose. In the next shot she is suddenly slouched to her right, with her right elbow resting on the table, leaning her head in her right hand; her left arm is lying across the table and she's holding her right arm with her left hand. Her vest is also hanging down, inside her blouse, showing a lot more cleavage than the previous shot. (01:07:45)
Continuity mistake: [Blu-ray] When Mandy goes to wake up Red and Chloe, Red wakes up with his right arm on the outside of the sofa. In the next shot, after Mandy has spoken to him, his arm is inside the sofa resting on his knee. (01:08:20)
Continuity mistake: [Blu-ray] When Red is rolling about on the floor after he has been shot, Chloe is asking him to get up and he has no blood on his mouth. In the next shot he suddenly has a lot of blood around and coming out of his mouth. (01:12:00)
Answer: The reason for Mandy and Emmett killing off the characters is pretty much left open for interpretation, but it seems the reason they killed them was because before Mandy became "hot over the summer" (as Dylan says at the beginning), Emmett and Mandy were treated like outcasts, and after Dylan's death, Emmett probably took a lot of the blame. It's possible that Emmett and Mandy were tired of how the popular crowd had treated them before.At the end, they made a pact to kill themselves. But after finding out that Emmett is just like the others, Mandy backs out and decides not to, but Emmett doesn't take it very well and decides to kill her too. Mandy fights him off, and she saves Garth, who seems to be the only one at the ranch who saw her as a human being and treated her with respect. So any of these reasons may have been motivation (although their actions are extreme), but overall there seems to be no obvious reason.
Hamster ★