Joshua Oppenheimer's 'Act of Killing' stirred a national debate in Indonesia over mass killings

"I'm always surprised that people even come to watch anything I make," Joshua Oppenheimer says, "so I was very surprised."

I'd asked him if the success of his documentary The Act of Killing had caught him unawares. His harrowing look at the genocide in 1965 Indonesia, when nearly a million alleged "communists" were massacred by paramilitaries following a political coup, has touched a nerve wherever it is played, even gaining a nomination for best documentary feature at this year's Academy Awards.

The Texas-born filmmaker, now 40, first stumbled upon the killings a decade ago, with the perpetrators still at large and the survivors forced into silence, years after these crimes were committed.

"To my astonishment, the perpetrators were boastful. I had this awful feeling that I had wandered into Germany, 40 years after the Holocaust, only to find the Nazis still in power," Oppenheimer says. "I had this feeling that this is such an important situation that I would give however many years it would take to address it."

Address it he has, with a film that literally turns the spotlight on those who carried out the heinous crimes. Co-directed with Christine Cynn and another filmmaker who has chosen to remain anonymous, the original intention was to create a more traditional documentary, using survivors' testimonies. But the idea morphed into something far more one-off when Oppenheimer met Anwar Congo and Herman Koto, two small-time gangsters who had taken the lives of thousands of "communists".