The chief looks at the tree and grunts, "Tree".
The Priest was pleased with the response. They walk a little farther and he points to a rock and says, "This is a rock".
Hearing this, the chief looks and grunts, "Rock".
The Priest was really getting enthusiastic about the results when he hears a rustling in the bushes. As they peek over the top, he sees a couple of natives in the midst of heavy sexual activity. The Priest is really flustered and quickly responds, "Man riding a bike".
The chief looks at the couple briefly, pulls out his blowgun and kills them.
The Priest goes ballistic and yells at the chief that he has spent years teaching the tribe how to be civilized and kind to each other, so how could he kill these people in cold blood that way?
The chief replied, "My bike".