It's doubtful there's a phone in the cabin on that land. I don't know it for a fact, it's just a hunch.
But even if they had a way to call the authorities, there's a strong possibility this guy wanted no witnesses. He has a history of trespassing, of threatening others with guns, and may possibly be involved in an unsolved murder.
I can speak from experience - when your life is suddenly threatened, unless a cop is nearby, you can forget getting any help from the authorities in time. They had every right to tell him as they would have any other trespasser to leave the property without any issues and without having to call the authorities to do it for them.