He was quick on the trigger, and bragged that he had killed 12 men not including Indians or Chinamen.
6 seconds sound clip from the Back to the Future Part III movie soundboard.
You can hear this line at 00:14:39.679 in the DVD version of the movie.
Quote context
[...]
- Marty, please don't stand there!
- I gotta get another picture.
- Shot in the back by Buford Tannen over a matter of $80?
- What kind of a future do you call that?
- Does it mention me? Am I one of the 12?
- Look. William McFly and family. Your relatives?
- My great-grandfather's name was William. That's him. Good-looking guy.
[...]