I recall something Miguel Littín told me five or six years ago. He had just filmed La tierra prometida in the Ranquil valley, a poor region of Chile.
The local peasants were "extras" in the scenes where there were masses. Some of them played themselves. Others played soldiers. The soldiers invaded the valley, and with bloodshed and fire, threw the peasants off the land. The film was the chronicle of the massacre.
The problems began on the third day. The peasants who wore uniforms, rode horseback, and shot blanks had become arbitrary, bossy, and violent. After each day of filming, they would harass the other peasants.
-- Eduardo Galeano, Days and Nights of Love and War