Shapes offer no hint of the horror within

At first glance, the painting looks innocent enough; a few abstract shapes and dotted lines that could be an aerial map or a stylised design.

In fact, it is a depiction of a killing field, a cattle station in the eastern Kimberley, where a white manager murdered a group of Aborigines in the 1920s - retribution for their theft of a bullock from a mob of cattle.

The artist Rover Thomas tells the story on a recording made a few years before his death in 1998. His voice is slow and steady, without a trace of anger. He chuckles at the ingenuity of one survivor, who hid from the gunman beneath a bullock hide.

"They never seen him," he says in a mix of Kriol and English. "That whiteman was busy - ptew ptew - shoot 'em up that other mob - killed them."