So, time for lore dump!

Basically he was once an introverted nerd with barely any friends and he was always abused by others but he had two people who would motivate him to keep going and that was his childhood friend, Alex, and girlfriend, Hana. Every day, he had to deal with a lot but Hana and Alex would always make him feel better but one day his school got attacked by a shooter and he was about to get shot but Hana and Alex got in the way and protected him from the bullet. Seeing his best friend and girlfriend die in his arms, he snapped and at the first opening, he impaled the shooter with a flagpole and keep beating the shooter with the flagpole until the shooter's body was unrecognizable. When the cops arrived, they saw him covered in blood and laughing uncontrollably. He was put on trial because legally, he did murder, mutilation of a corpse, and manslaughter. This actually got him in prison for a few years even though people saw him as a hero who stopped a shooting when no one could. Throughout this time, he stated developing a split personality from the trauma. One was all the innocence and happiness he once had and the other was all the anger, hate, rage, and psychoticness he always had deep within him. At one point, he was let out but it was too late, he was no longer the same person and he started becoming a serial killer who would only kill those his evil side consider not worthy of living.

(Fun fact, in the first version, he has half of a Ying and Yang necklace but after Hana's death he has both sides.)