Blocking a road, arms prominently displayed & at the ready, is a threat.
Put yourself in his position and tell me you wouldnt consider it a threat.
Ive been there, and did.
I wouldn't keep running toward it. I most certainly would not try to take the shotgun away from the guy.
Perhaps he didn't see it as a threat? He certainly behaved as if he didn't understand the threat represented by a man with a shotgun.