This brave, mind-bogglingly horrific yet mesmerisingly surrealistic documentary has had jaws dropping at its various film festival outings around the globe including Sydney and Melbourne.

Executive produced by two giants of the documentary world, Werner Herzog and Errol Morris, who signed on after seeing early edits, the film is a hauntingly innovative expose of a crime of genocidal horror in Australia’s backyard – the mass liquidation of Communists by the Indonesian dictator Suharto in 1965 following a failed Communist coup attempt.

US-born filmmaker Joshua Oppenheimer had initially tried to make a film based on the experiences of the surviving victims. But finding them reluctant to speak he instead tracked down some of the killers, a motley group of ex- gangsters and paramilitary members, and encouraged them to both talk about and re-enact their unpunished crimes for his cameras in scenes both gruesome and weird.

The film doesn’t glorify or excuse the killers, whose reminiscences are especially confronting in being so insouciantly expressed, but seeks to understand how the perpetrators have managed to live with their actions. The result is something we’ve never seen before – a new type of film – call it psycho-documentary – that’s not just about mass crimes but the state of mind that produced them.

The Act of Killing opens in select cinemas nationwide October 3.