Yes, he really killed Lennie. In order for Lennie to be "put down" mercifully, George had to do it before the angry mob did. Consider how Candy's dog was shot by Carlson earlier in the story. Candy laments not having been able to do this deed himself. In contrast, George does get the chance to put down his own "beast" or best friend.
*All quotes are taken from the Penguin edition of "Of Mice and Men" (1993)
Lennie is telling Curley's wife about the rabbits he and George are going to get. Lennie likes to touch soft things. Curley's wife is compelled by Lennie's childish nature: " 'You're nuts,' she said. 'But you're a kinda nice fella. Jus' like a big baby. But a person can see kinda what you mean. When I'm doin' my hair sometimes I jus' set an' stroke it 'cause it's so soft.'" (Pg. 90)
She lets Lennie touch her hair to see what it feels like, but Lennie gets carried away. She tells him that he will mess it up, but he continutes to stroke her hair. Finally, she starts to get upset, and starts to yell. Lennie doesn't like yelling, so he puts his hand over her mouth:
" 'I don't want you to yell. You gonna get me in trouble jus' like George says you will. Now don't you do that.' And she continued to struggle, and her eyes were wild with terror. He shook her then, and he was angry with her. 'Don't you go yellin',' he said, and he shook her; and her body flopped like a fish. And then she was still, for Lennie broke her neck." (Pg. 91)
George knew that Lennie didn't intentionally kill Curley's wife; George also knew that Curley would have Lennie killed--Lennie was misunderstood. George took Lennie down to the lake, and had him think about the rabbits and the ranch--Lennie was thinking about things that made him happy. George killed Lennie to save him from a society that misunderstood him.
In John Steinbeck’s Of Mice and Men,Lennie is a mentally challenged and strong migrant worker who travels with George, his smart friend. When the body of Curley’s wife was found at their new place of work, everyone knew Lennie had done it. Curley and the other men went to find, lynch, and kill Lennie. George knew that Lennie was by the pond and he went there told Lennie to look to the hills and imagine their farm. While Lennie was looking away George gave the final blow. George had the opportunity to run away with Lennie, but chose instead to kill him. The reason for this was to make sure that Lennie died happy. Lennie would soon be found, punished, and killed by the other men so George had to make the decision to end Lennie quickly. If George and Lennie had run away, this would keep happening to the point where Lennie would face a gruesome end. The reader knows this because Lennie had done the same with a woman’s red dress and the puppy. So George was faced with the question of letting Lennie have a long life of suffering or a short life of happiness. George made the right decision to let Lennie die dreaming about his farm. Like Candy’s dog, Lennie was beginning to hurt himself and it would be cruel to let him suffer more. Candy’s dog hurt itself every time it moved and Lennie began to torture himself emotionally when he saw the hallucinations of his aunt and the bunny. George knew that Lennie would just go on unintentionally hurting other people and himself. George made the right decision in putting Lennie down. However, he had to live with his decision for his entire life. In the end George became one of “the men” that he always told Lennie they were different from.
Yes he did, it was sad...it was at the end right after Lennie accidently killed Curly's wife...she had let Lennie pet her hair because she was bragging about her hair being soft and Lennie had told her that he liked to pet soft things, so Curly's wife had let Lennie pet her hair. Lennie got excited and was happy but Curly's wife was repeatily saying "don't mess it up" over and over when Curly's wife seemed to have enough she told him to stop and let go, but Lennie didn't want to let go so she began screaming and Lennie said, "dont scream i'll get in trouble" he was holding her mouth shut and she was trying to get away and he kept holding on and all of a sudden he shook her and her neck snapped...George and Candy found out that Lennie had done this and they went searching for him so they could kill him. George had knew where Lennie was and Lennie thought George was mad and George said he wasn't but he pulled out a gun while explaining the dream house and had Lennie look away into the sun so "he can see it" and Lennie was all happy and George was talking about the house and Lennie said, " And I get to tend the rabbits" and then the gun went off, George had shot Lennie.