Bear in mind I wasn't there nor am I a moose expert- but technique for animal charges is generally to make yourself appear larger than you are, which I saw him do. He stands up and claps. He makes noise to try and drive it away.
Also he seems to stop plenty far back from what I can tell- the moose approaches. It doesn't look like there is much room to maneuver- he clearly is on a trail. Pause the video near the beginning and notice the trees along the trail. Secondly, when you take a stopped snowmobile and get into deep powder it is *very* easy to get stuck.
Also I can see why he revved it- like in a car, he assumed that by making himself larger and gunning the engine he would scare the moose away. I am not an expert on moose behavior, but I'm not sure I would have done anything differently.
Finally after he was bluff charged, and then actually attacked, he pulls the gun when the moose turns back at him.
He didn't pull the gun as soon as he saw the moose, he didn't pull it after a bluff charge- he waited until he was actually attacked.
It does bother me as well that he didn't go back and check on the moose or finish it- then again, he might have just wanted to GTFO of there, and reported the incident to wildlife officials- that would actually be the proper thing to do after such an event. It *certainly* could be the moose got back up after the initial shock of the hit and went off the trail- either way a guy on a snowmobile is not setup to track a wounded, possibly aggressive moose.
It's sad- but when we go into nature these things can happen.
