How does John Steinbeck use imagery to describe the "brush" in the last scene of Of Mice and Men?

Up to this point, the "brush" has been a safe place for Lennie, a place for him to discover the small animals he loves so much. Lennie always remembers that in case of any trouble, he is supposed to go hide in the brush and wait for George to come take care of him.

As the novel comes to a close, George and Lennie meet near the brush, and of course there is trouble: Lennie has accidentally killed Curley's wife, and now an angry mob is on its way to exact revenge on Lennie. Knowing they can't escape, George is determined to end his friend's life humanely before he can suffer at the hands of the mob.

Here's how the narrator employs sensory imagery with the brush to build suspense and create realism for the scene. First, he describes blue shadows, the approach of evening, and the spooky sound of "crashing" in the brush from far away:

The shadow in the valley was bluer, and the evening came fast. On the wind the sound of crashing in the brush came to them.

We know now that the mob is on its way. And the auditory imagery of the brush intensifies, signalling how close it's coming to Lennie:

There were crashing footsteps in the brush now.

After ending his friend's life, George knows that the mob is an instant from bursting into view because he can hear it:

The brush seemed filled with cries and with the sound of running feet.

All these sensory descriptions of the brush and how it rustles, how it's "filled with cries," create a sense of encroaching pandemonium in this final scene. We hear the sounds as if we were there with George and Lennie, and as the sounds intensify, we become more and more tense, knowing that for these characters there's no escaping the violence.