Found

As if his life wasn't complicated enough, Marty, a bullied twelve-year-old horror-movie aficionado, makes a horrifying discovery: undeniably, his big brother, Steve, is a real-life serial killer. Now, Marty not only has to endure the relentless bullying at school, and his neglectful parents, but also he has to deal with Steve's horrible secret--a terrible discovery that threatens to alter, irreparably, his already messed-up life. For his age, Marty has seen many horror movies; however, none of them matches the raw brutality of the film called Headless (2015) in his violently protective brother's hidden VHS collection. Does this astounding revelation explain Steve's motives?