"Dry September" is suffused with violence. Much of the violence is rumored, hinted at or implied. It is left to the reader to decide what may have occurred. The explicit violence in the text, the initial beating and abduction of Will Mayes by a vigilante group, and John McLendon's abuse of his wife, are all described with stark, minimalist precision. Much of the story's violence is in the form of psychological pressure, and social pressure, and is exposed as the violence of a community deeply divided along class, racial, and gender lines. The violence of nature is also at work. After some two months without rain, in the hottest part of the Mississippi summer, Jefferson is on the verge of self-combustion. All these factors converge in this tragically violent tale.
While the violence against Will by the vigilante mob is criminal, Will's violence against them is justifiable because it's in self-defense.
Henry jumps from the car to avoid being forced into doing further violence to Will, but by abandoning Will, he also does violence against him.