Continuity mistake: Near the end when they're entering the Mexican village, Billy's coat disappears as he rides through the gate. (01:17:45)
Continuity mistake: The knife in the post is first pointed up, then pointed down.
Continuity mistake: When Tunstall arrives at his place with Billy for the first time, Tunstall is clean shaven. At dinner that same night, he has a mustache.
Continuity mistake: When Billy is thrown out of window in a chest, he lands on the left side of the window / porch, but when he jumps up, he's on the right side. (01:38:50)
Chosen answer: He may have. When Billy started whistling, the bounty hunter's face changes. He continues to speak to Billy in a dismissive tone, but does eventually pull the trigger (although Billy had unloaded the pistol). Hard to believe he would just shoot some mouthy kid in a bar.