Connor remembers well the night it happened, the full moon hanging in the sky as its pale light was cast through an open window as he slept. He awoke in the dead of night not himself, but something different, more monstrous, canine, a curse of lycanthropy. It shocked him to his core, surely this was just a bad dream right? He slept, and in the morning he was his usual self, human without a patch of fur on his body.
Though it got worse, every full moon it was like this, he could never remember what he did or where he went during these episodes. Eventually he was never even fully human by morning, his transformation lasting longer and longer into the day. Soon, even waxing or waning moons caused him to change, his personality too morphed into that alter ego of his werewolf side.
months of this persisted, and soon, he never did change back to a human. He saw this as a curse, he was hardly even himself anymore, but this is what he was, and learned to embrace it.
I love both modern and fantasy stories in equal parts, this character and background is quite flexible to fit whatever you may want with this werewolf ;)