Arthur was quick, even as he forced every breath in and out of his body, he drew the Scholfield revolver from his belt, when the stranger walked up. He wasn't going to let the horse be target practice again. But... it was holstered shortly after. Once he got a good look at John, he could tell from where he stood that he wasn't one of the Pinkerton men.
"Sorry, thought you were someone else." The words came torn from his throat, as if they'd forced their way out. But they were followed with a fit of coughing that had him turning his face into the horse's hide. He didn't think TB transferred from human to beast. But it was better than risking someone else getting it. His fingers tightened on the stallions mane, as blood speckled his hide.
When he could breathe again, though harsh as it was. "Nope. Not okay. Tuberculosis. I reckon it's done come to collect it's due." The gentlest way that he could say that he was sure that death was clinging onto his hindquarters, and pulling with all it's might.