You don't see them till it's too late.

There's a log or something across the road, if it's a coach, or else the driver's walking his horses up a steepish hill.

Just at the worst pinch or at a turn, some one sings out 'Bail up.' The coachman sees a strange man in front, or close alongside of him, with a revolver pointed straight at him.

He naturally don't like to be shot, and he pulls up.

There's another man covering the passengers in the body of the coach, and he says if any man stirs or lifts a finger he'll give him no second chance.
Just behind, on the other side, there's another man--perhaps two.