If you read the account from Cheney's FOXNews interview, I think that Cheney was being very gracious and a gentleman by accepting responsibility. In my opinion Whittington should accept alot of the responsiblity as well. Here is why:
The are hunting in pretty thick brush. A covey of quail gets flushed by a guy on horseback and Whittington shoots one, it goes down in the brush and he goes to look for it. While he is looking for his bird, the rest of the group get in the pickup trucks and go down the dirt road another 100 yds. , where another guy on horseback has flushed another covey of quail.
Cheney has one in his sights, he is swinging his shotgun with the flight of the bird, focusing on the bird & boom... . oh damn, where the heck did he come from! An accident pure & simple, sounds to me like Whittington was pretty stupid to be where he was. Sure as a hunter Cheney had to be aware of his surroundings, but maybe he was aware, but then in the few seconds in which he was focused on the bird, Whittington came popping up out of the brush.