What does Lennie think and do after he kills Curley's wife?

Lennie's world basically revolves around George. Immediately after accidentally killing Curley's wife, he thinks about George and he remembers his friend's instructions about going back to the spot between the Gabilan Mountains and Salinas River which was the setting of chapter one. He knows he has done something wrong but only views it within the prism of what George will think. He says,

“I done a real bad thing,” he said. “I shouldn’t of did...

Lennie's world basically revolves around George. Immediately after accidentally killing Curley's wife, he thinks about George and he remembers his friend's instructions about going back to the spot between the Gabilan Mountains and Salinas River which was the setting of chapter one. He knows he has done something wrong but only views it within the prism of what George will think. He says,

“I done a real bad thing,” he said. “I shouldn’t of did that. George’ll be mad. An’ . . . . he said . . . . an’ hide in the brush till he come. He’s gonna be mad. In the brush till he come. Tha’s what he said.” 

Lennie takes the dead puppy with him and goes out of the barn leaving the dead girl in the hay. 

When Lennie gets to the "brush" in chapter six, he has two hallucinations. The first is of his dead Aunt Clara who admonishes him for not listening to George. She says,

“I tol’ you an’ tol’ you,” she said. “I tol’ you, ‘Min’ George because he’s such a nice fella an’ good to you.’ But you don’t never take no care. You do bad things.” 

The second is of a giant rabbit, which some critics have said is symbolic of Lennie's animalistic nature, but also reflects his obsession with petting soft things. The rabbit comes alive and scolds Lennie telling him he isn't fit to tend rabbits and threatening that George will leave him because he does too many "bad things." The rabbit says,

“Well, he’s sick of you,” said the rabbit. “He’s gonna beat hell outa you an’ then go away an’ leave you.” 

The passages reveal that although Lennie is mentally challenged and remembers very little he does have a conscience. He feels guilty over what he has done. His guilt, however, is only about what George will think. When George arrives Lennie believes George will "give him hell." He never realizes the serious nature of his actions and what the consequences will be. He focuses on George who tells him about the dream one more time before killing with him with Carlson's luger.