The shaman of an African tribe was a superstitious man. When his tribe found the Fourth Doctor, Sarah Jane Smith and Harry Sullivan standing over the dead body of Mposi, he thought they had summoned a duba to kill Mposi. He was angry at the chief's decision to let the Doctor hunt the duba.
When the Doctor and his companions were able to get to the TARDIS, the shaman realised the chief must have helped them, and incited the rest of the tribe to kill the chief. (PROSE: To Kill a Nandi Bear)