Jeff the Killer is the titular villain of the Creepypasta story of the same name. He is based off F**kS**t. He was originally a young latent psychopath who brutally beat up a trio bullies, Randy, Keith and Troy, who were picking on him and his brother Liu in the town they had just moved to. Liu took the blame for it and was arrested, sending Jeff into a depression. Later, the bullies attacked Jeff again at a party, and Jeff killed all three of them, but not before getting covered in bleach and lit on fire by Keith as he died. During this fight, Jeff's mind permanently snapped.
When Jeff woke up, he was in a full body cast at the hospital. When the bandages were taken off, it was revealed that his face had become disfigured and ghastly pale from the burns, with bright red lips and a leathery texture. Jeff said that he liked his face this way and laughed hysterically, but the doctor foolishly thought that this insanity was just the result of the painkillers and let Jeff and his family (including Liu, who was released) go home.
Later that night, Jeff's mother found that he had carved his face into a permanent smile so that he would no longer have to exert energy to smile, as he put it, and burnt off his eyelids so that he could always see his face. Jeff's mother went to her husband to tell him that their son had gone completely mad and needed to be killed, but Jeff caught them and knived them to death. This woke up Liu, who confronted his brother but was killed as well, with Jeff telling him as he was about to plunge the knife into his body, "just go to sleep." Sometime later, an "ominous unknown killer" emerged and went on a killing spree. A boy who was lucky enough to survive the killer's attacks described the man as having inhumanly pale skin, a hideous smile, and dark, ominous, constantly open eyes. When he tried to kill the boy, he told him to "go to sleep."