- "What is it, Marty? You look like you've seen a ghost."
- —Doc's response to Marty's sudden outburst
- " 'Shot in the back by Buford Tannen over a matter of eighty dollars?' What kind of a future do you call that?!"
- —Doc Brown to Marty McFly about the tombstone
Dr. Emmett Brown's tombstone became a reality after he was shot in the back by Buford Tannen on September 5, 1885 over a matter of eighty dollars, seventy-five dollars of which involved Tannen's stolen horse that threw a shoe — and which Tannen subsequently shot, forcing him to steal another — and the remaining five dollars for a bottle of fine Kentucky Red Eye whiskey which got smashed in Tannen's fall from his steed. The tombstone was erected in memory by his love Clara Clayton who took care of him for two days while the bullet that entered Doc killed him slowly. After he died on September 7, he was placed in Boot Hill Cemetery, and the tombstone was engraved with ERECTED IN ETERNAL MEMORY BY HIS BELOVED CLARA.
It remained there for seventy years, ironically close to the DeLorean time machine he hid in the Delgado Mine, until Marty McFly and his 1955 self stumbled across it in horror. Marty took a photograph of the tombstone using Doc's camera and took it with him to 1885. On the night of the Hill Valley Festival where Doc was shot in the first timeline, Marty prevented it from occurring by intercepting the shot with a Frisbie pie tin thrown in the style of a frisbee. The bullet that was fired only managed to hit the hat that Doc was wearing at the time and send it flying off his head. This prompted Tannen to challenge Marty to a duel on Monday morning at 8:00 a.m.
From this point on, the inscription on the photograph began to vanish and the next morning, Doc theorized that it might have been CLINT EASTWOOD on the tombstone instead with this change of circumstances. By the time of the duel, his alias appeared on the tombstone. Marty had then made the decision not to face Tannen. But he changed his mind only to save Doc, who had been taken hostage by Buford's gang. Tannen shot Marty down, but Marty survived the gunshot by wearing an iron stove door on his chest as a makeshift bulletproof vest. Marty then knocked Tannen headfirst into the tombstone, breaking it in half, before knocking Tannen into a cart of manure.
With Tannen defeated, and the tombstone destroyed, Marty saw it vanish completely from the photograph before his eyes.