I posted a thread this morning that looks like it was combined with another that I took zoomed in screen shots of the shooting. I agree with Jeff, he did initially have his hands up (after trying to run down an agent) but then put them down into his jacket before he was shot. He could have been reacting to an earlier shot or he could have been reaching in his jacket, it is hard to tell without audio.
If he was trying to run down an agent, why not just crash into the vehicles blocking the road? Did he see agents hiding out in the trees and decide to go for one of them instead? Seems to me that he was trying to go through the snow around the roadblock and didn't make it.
And yeah, he could have been reacting to being shot when he brought his hands down. Getting shot would also explain him stumbling in snow that he seemed perfectly able to navigate when his hands were outstretched.
Saying he put his hands down into his jacket before he was shot implies that you know when he was first shot. If they started shooting him before he brought his hands down, that would corroborate witness statements that the police shot him while his hands were up. But those aren't the right kind of witnesses...