Not so much a mistake, but just some darn good filmmaking. Near the end of the film Charlie Smith(Jack Nicholson) is having a shootout with J.J.(Jeff Morris). J.J. , carrying a loaded shotgun, is trying to escape Charlie's gunfire outside a barn. J.J. runs into a wire or equipment obstruction and falls to the ground accidentally triggering the shotgun and blowing out his own brains. Some good stop-motion photography is employed here and an obvious dummy or mannequin is revealed as J.J. gets the shotgun blast. Nicholson's character Charlie Smith stands aghast as the dead J.J.'s brains ooze out and shotgun smear covers his body. The stop-motion dummy is similar to the scene in "Casino"(1995) where Robert DeNiro gets into his Cadillac, turns the ignition, and the car turns into a fireball revealing an obvious dummy/mannequin.
