Why does Connor rescue lev

In chapter 4, Connor says that he decided in "a split-second decision" to rescue Lev because he felt that he needed to "balance" the harm he had already done with "something decent." Connor says that he was already responsible for the bus driver's death and "maybe more," and that, even "if it risk[ed] everything," he had to do "something good to make up" for the misery he had caused. His decision to rescue Lev was thus motivated mostly by guilt and by a perhaps misplaced hope that he could make up for one death by preventing another.
After Lev is hit with a bullet meant for Connor, Connor picks him up, "flips him over his shoulder," and carries him into the relative safety of the woods. Connor then decides that Lev can't be trusted and so ties him to a tree. Later in the story, Connor dislikes Lev so much that he has to restrain himself from hitting him. He tells himself that he "didn't rescue the kid just to beat him up."