Why does the Abame clan kill the white man?

The Abame clan came across a lone white man with on an “iron horse” (a bicycle). They were surprised and offended by his inability to communicate with them. Their oracle declared that he was the first of many white men to come that will destroy the clan. The clan took this to heart and killed him tying his iron horse to a tree “because it looked as if it would run away to call the man’s friends.”