A film about the modern expulsion of few native Americans

A film from the 1980s or 1990s, set in that same era. Native Americans and cowboys are holding a celebratory ceremony, reenacting historical battles on horseback. One of the cowboys uses a real gun and fires a shot (I’m not sure if he kills a Native American). A small group of Native Americans notices this and rebels. A chase ensues, with a large group of cowboys and police pursuing a few Native Americans through the wilderness. The final scene shows two or three Native Americans charging forward while a military helicopter bears down on them. I wasn't in school when I watched it on TV, so my memory of it is quite hazy.