Amnesia
He would flinch when someone tried to give him a high five (the program he was in advocated for positive reinforcement, including positive physical interactions), but he couldn't remember the reason he was afraid.
He would be filled with rage every time he saw a skinny blonde girl, but he didn't remember the drug addict mom that gave him that hatred. He didn't remember the dozens of other blonde girls that he had killed, all as a result of his warped childhood, an unholy combination of innate mental illness and abuse.
He still had the violence. The rage. The trauma. He just couldn't remember the source. He would wake up from nightmares sweating and afraid, but couldn't picture the face that was haunting his dreams.
He would be escorted from place to place, but he didn't mind. It was all he'd ever known. The only thing he couldn't understand was why so many were afraid of him, why so many people called him names.
He saw a therapist for his anger. The therapist would nod and hem and haw, but when the thirty minutes were up he was still angry and the therapist was fifty dollars richer.
Sometimes he'd explode and punch walls or break his knuckles against the metal paper towel dispenser in the bathroom. But he never hurt anyone.
When he was seven he saw his mother stab a man in a parking lot. The man was her dealer and demanded a higher price. She got pissed. She took his entire stash and blew through it in four days. The man was never shown on the news. It taught the young boy that murder was simply a part of life. It also taught him never to get between Momma and her drugs.
When he was twelve his mother flew into a psychotic rage and pushed him down the steps. He broke his ankle and couldn't move for two days. He laid there at the bottom of the steps and learned to shut off the pain. He still walks with a limp, but he no longer remembers why.
He had only ever known violence. So why was it surprising that he grew up to become violent? And yet, even without his memories, the feelings were still there. The fear. The anger. Now that he knew more than just violence, it was too late: his habits had already been learned, his childhood had already been lived and then forgotten. To truly fix him, they'd have to start from conception. Seize him from the womb and set him loose in a world that taught him love and compassion instead of vitriol and violence.
Erasing the memories wouldn't erase the experiences. They still happened, and he still feels its aftereffects. Only now, he has no rationale for the way that he feels. And no one can give him any answers.
One day, this lack of a reason will cause him to snap. He will kill again.
Until then, he will keep flinching every time someone tries to give him a high five. And he will keep wondering why he is so afraid.