I broke the both my ankles, and it was the same talus bones that tanner broke. I got up and was walking around, trying to kid myself that my season wasn't over. My friends told me to sit down and stay warm until they got ski patrol.
So, with shock, and adrenaline, you're not really thinking straight and the temptation is there to try and walk it off. Telling someone to stay still (especially considering the severity of Tanners crash and possibility of spinal injuries) is really one of the most senisble things to shout until a medic got up there to him.