As we lead up to the start of this year’s Toronto International Film Festival, which kicks off Thursday night, I need to post some remaining documentary trailers I haven’t yet shared. The one above is for Joshua Oppenheimer’s The Act of Killing, already a highly anticipated film that has just boosted its buzz by knocking them dead at the Telluride Film Festival over the weekend.

Maybe knock them dead isn’t a good term for something involving the mass murder of a million people in 1965. Well, the question of taste is at least appropriate. Executive produced by Werner Herzog and Errol Morris, both of whom lent their names after being stunned by the doc , The Act of Killing looks at Indonesian Death Squad leaders who are still celebrated as heroes today and feel no guilt about the horrible atrocities nearly forty years ago.

A.O. Scott of the New York Times says the film has “an openness and relish that sometimes inspires queasy, horrified laughter.”And Indiewire’s Eric Kohn tweeted that it’s “possibly the most unsettling movie about mass murder since Shoah.” If we’re looking for comparisons, without seeing the doc I’m reminded of Enemies of the People, a recent work profiling the unrepentant Khmer Rouge deputy Nuon Chea.

Yet The Act of Killing looks like nothing I’ve ever seen before (I’m especially intrigued by the costumes and film-within-the-film), as well as probably the most disturbing doc in some time. I like provocative, ethically challenging, discussion-prompting docs, so you can bet this is one I’m really looking forward to. Put it on your radar if you like what you see, as I’m sure we’ll continue hearing about it.

Don’t listen to me (again, I haven’t yet seen it). Listen to Herzog, always a great salesman:

“I have not come across a documentary as powerful, surreal, and frightening in a decade.”

For more info, check out the TIFF listing, including the program notes by Thom Powers. The doc makes its Toronto premiere this Saturday night.