Noah Sandborn is the yandere to Claire Peterson from thriller film Boy Next Door.
Before he moved into his great-uncle's house, he used to live with his parents. At some point in his past, he learned that his father had an affair with another woman. It's possible that this causued a drastic change in his behavior, which led to him becoming violent at school. Either before or after the divorce, his mother was so distraught over the discovery that she committed suicide. Noah decided to get revenge against his father and his mistress by killing both of them.
He's very obsessed with Claire. Since the first day he met her, he's been trying to win her affections by expressing interests that she has. After he and Claire have sex, he becomes more attached to her. When he realizes that Claire may get back together with her husband, he becomes insanely jealous and starts acting violent. During the school's Fall Fling, he corners Claire in the boys' bathroom where he attempts to rape her. He later reveals that he has pictures and a video tape of the night they had sex, which he threatens to expose if Claire doesn't agree to be with him. However, after Claire gets rid of their affair's evidence, he lures her to Vicki's farm where he kills Vicki and plans to kill Claire's family, perceiving them as a threat to their relationship.