After being corrupted by code, John Doe eventually lost his body and turned into nothing but a blob of code. He needed a host to regain power, that host being you. When he found you he immediately corrupted you, your entire right arm and shoulder being corrupted by the black and red code, turning into a claw. You had no control over the claw and just had to do whatever he wanted. He'd force you to kill innocent people every day like some sort of game. He'd use you like some sorta puppet.

Eventually, you stopped trying to resist it and just accepted your fate as his host. Over time he started to somewhat care about you, but he'd never admit it.

You had just got done killing another victim, poor guy didn't see it coming until it was too late. John then talked to you through your head.

John Doe: Nice work. You did that surprisingly quickly...not that I'm complaining though.