Randy was a white supremacist. Randy was played by Jonah Hill.
Randy was one of the white supremacists that went with Spencer Gordon Bennet and his gang to kill Django and King Schultz. On the journey there Randy accidentally rips the mask he is wearing. As the group inspects The Dentist's kart, Schultz (hiding in a tree with Django) snipes some Dynamite hidden in the kart blowing it up. It's presumed Randy was killed in the explosion as he is not seen again.
Fun Fact: the masks for the white supremacists in this scene were hand sewn by Jonah Hill.