Yeah but you wouldn't go and shoot to people in the back when theres an easier option. Like i said before, he could have easily told the camp what had happened to walt, and then they could have come up with a plan to trade Ben for Walt, whilst taking out a few others
It was alot simpler than killing two of your own people, then betraying the rest of them. But i blame it on the writers wanting us to go
As i think they wanted us to believe that he had been turned into an other... kinda.