Django Unchained: What was the audience laughing at during this particular scene?

I saw this movie at the cinema recently, and was momentarily distracted during the scene in which Shultz shoots and kills Ellis Brittle (the guy running through the field).

The cinema audience started laughing after Shultz fired the shot, from what I thought (as I said, i was distracted) was a comment made by Django right after Shultz fired the shot. However upon reading page 34 of the script (linked off the first post in this thread), I can’t see any dialogue between Shultz and Django after Shultz fires the shot. The next words spoken are by Shultz to the gathering crowd, which I remember clearly.

So… to those who’ve seen it… any idea what might have drawn audience laughter between the moments when Shultz takes the shot, and then him saying “Everybody calm down!..”?

Shultz: You sure that’s him?
Django: Yeah.

Shultz: Positive?
Django: I dunno.

Shultz: You don’t know if you’re positive?
Django: I don’t know what positive means.

Shultz: It means you’re sure.

Django: Yes.
Shultz: Yes, what?

Django: Yes I’m sure that’s Ellis Brittle.

(Ellis gets shot while riding through cotton field on horseback)

Django: I’m positive he dead.

Thank you, Coriolanus.