When the cowboys go into the barn and discover all the horses are dead (killed by the snakes) they hear a commotion in the saloon and all run back out into the street. When they leave, a "dead" horse lifts its head up and looks around, probably startled by the noise of the actors running.
Tannen states that the safe he built for the bank is impenetrable, yet Will is able to put a hole through the wall with a single shot.