- Gang member: "Careful, Buford, you ain't got but one bullet with that."
- Buford: "I only need one."
- — Outside the Palace Saloon.
- "Supper time on Monday? Two days to die? But Doc wasn't ready — especially now that he had found Clara. He had been too smug, confident that he could escape this villain with the use of the time machine. But now he realized the fact that he died on Monday didn't mean he had to be shot on Monday. / Doc could feel the sweat run down his forehead. Tannen had his derringer pressed right against Doc's innards. The minute Doc tried to escape, or make any kind of move against him, Tannen would simply pull the trigger. And Doc, in this day before wonder drugs and modern surgery, would slowly bleed to death. / Emmett Brown took a ragged breath. Wasn't there something somebody could do? Or was he already a dead man?"
- —From Back to the Future Part III by Craig Shaw Gardner (quote, page 123)
A derringer was a small pistol meant for close range, and could only hold a single bullet.
Although the derringer could only hold a single bullet, one shot was all Buford needed. When Buford found Dr. Emmett Brown at the Festival, he held it up to his back and warned him that the last man he shot took two days to slowly die from the bullet wound.
Upon being stomped on the foot by Clara Clayton, Tannen drew his derringer towards Doc and aimed to fire. Marty McFly diverted the aim with a Frisbie Pie Company tin by throwing it like a plastic frisbee flying disc, causing the derringer to go off harmlessly in the air — wasting Buford's only shot and saving Doc. However, the bullet struck Doc's hat and knocked it off his head. When Doc wore the hat later on, a bullet hole was visible.