The barber held the razor poised above the half-risen client. (1.12)
It's interesting how Hawkshaw, the man trying to keep things from escalating to violence, presents such a violent figure at this moment. This brief moment contributes to the highly volatile mood of the scene.
From his hip pocket protruded the butt of a heavy automatic pistol. (1.45)
As we discuss in "Symbolism, Imagery, Allegory" the gun seems to foreshadow Will's death. But, since we don't know for sure that Will dies, or if he was shot, we can't state this conclusively. We can say that the gun lets us know, in case we weren't sure, that McLendon's might well be feeling murderous.
It was twelve years now since she [Minnie] had been relegated to adultery by public opinion. (2.4)
Here public opinion is violent. By exerting social pressure to break up Minnie's relationship with the banker, and then punishing Minnie for her transgression, the community does her violence.