The line between reality and fiction is ripped apart by Canadian writer-director Matt Johnson in this ramshackle yet inventive first feature, which arrives with the effusive backing of Kevin Smith. The Dirties was shot for just $10,000 with virtually no script and the sometimes unwitting participation of passers by. Unafraid to launch himself in at the deep end with his debut, Johnson's film depicts the lead up to a high-school shooting.

The Dirties follows two outsiders, played by Johnson himself and Owen Williams (both go by their own names here), as they enact fictional vengeance on a gang of bullies for a film class project. When their hyperbolic short is mocked by their peers Matt decides to execute the revenge for real; his targets are a group known as The Dirties. Owen meanwhile is more interested in pursuing a girl, Chrissy H (Krista Madison).

Although it's pitched as a black comedy there's a notable absence of wit. Instead we get the embarrassing antics of two clueless teens – whose student-film-within-a-film is an incoherent shambles. It's a credible portrait of the birth of a psychopath as the film sheds its at first gawky skin for something altogether more sinister, with people's dismissal of Matt allowing him to go about his macabre preparations in plain sight.

The way The Dirties deals with the question of the ever-obvious, handheld camera is problematic – there's the occasional reference to those filming but it's often not clear why they're doing so. There's something chillingly enigmatic about the camera's presence at points, but ultimately it's a confused approach. Yet The Dirties is eerily convincing as a character study and the leads' awkward performances fit the roles. This isn't a film that's particularly easy to enjoy but that doesn't mean that there isn't much here to admire.

THE DIRTIES Trailer (2013)