Three Prisoners (2000)

"Not actually called Tres Oreos as most people think."

Three prisoners escape from a train or something. And I think they had to go find a treasure. They shoot some people at some point. Also, one of them had a retarded kid that either got shot or shot someone. Most of the movie takes place on a farm with some old people. Maybe they are holding the old people hostage? That's all I remember.