Schemer (2010)

After a group of teenagers discover one of their friends lying dead on a river bank on one of the hottest days of summer, a story of jealousy, insecurity and peer pressure gradually unfolds. Group leader Caesar is able to magnify - out of all proportion - the small grievances that each of Jessie's friends bear towards her and transforms them into a general and pervasive hatred that leads ultimately to her horrible, senseless killing.