This. Right here.Do you have any idea where they might be parking? If they come back, block them in and call the local Sheriff or PD.
As much as I'd like to be the guy that says go get 'em and run them off, it may not be the best idea. If they're bold enough to trespass, what else will they do? And don't always assume they're hunting. We went for a midnight stroll in our woods once and stumbled across someone's trail from the road to the neighbor's property, marked by glow in the dark paint. I suspect they were up to something... suspect.