When Pepe flees after tearing down the poster of the Imperial Decree, he is shot in the back from a distance. But when the wounded Pepe is brought to his father, the bullet wound is now in the front of his body on the right side of his chest near the shoulder.
About 72 minutes into the film, the Imperial Mexican soldiers are committing executions in a village. Pepe, the young boy, tears down a posting of an Imperial Decree and flees. The commander of the Imperial soldiers draws a Colt Model 1873 Single Action Army and shoots the boy down. As the film is set in 1865, this pistol will not be invented for another eight years.
When Napoleon lll is informed in a letter that Robert E. Lee has been defeated at Gettysburg, he responds by paraphrasing Lincoln's famous Gettysburg Address by calling democracy as government for the people, by the people, etc. He couldn't have known Lincoln's rhetorical flourish because the speech wasn't given until mid November 1863.