The Blackfoot nation was a hostile tribe, and posed an ever-present threat to Carson's safety. A Blackfoot warrior once injured Carson in the shoulder. This was the worst injury he received in his life. He hated the Blackfeet, and killed them at every opportunity. Historian David Roberts has written: "It was taken for granted that the Blackfeet were bad Indians; to shoot them whenever he could was a mountain man's instinct and duty." The Blackfeet did not like whites. They were convinced whites were trying to take over their hunting grounds. In addition, the Blackfeet wanted the valuable horses owned by the whites.