How did thresh kill clove in the hunger games?

No one knows. Katniss just hears about it when they see the dead tributes' faces projected in the sky.

Yoyo_963: It says nothing about his death in the book BUT Suzanne Collins (the author) was working with the director and in the movie he dies by a mutt. In the book he was killed by Clove since later on on Clove recovered the package that Thresh stole