Even in a place where they were expected to kill each other, Ian had still expected some human decency. So he was surprised at the other man deliberately ignoring him. Surprised enough that he'd taken his eyes off the bison and it came down on him.

He was lucky in that it landed on one of his legs, doing some damage, if not breaking it, and caught a glancing blow to his chest. It was enough that when Ian cried out in pain he then discovered that breathing was a lot harder than it was. He struggled to get a small amount of breath in before he coughed.

That just seemed to enrage the bison more.