I can understand not wanting to lose established characters from a game, but I don't see how issuing them to a succession of new players is better than letting someone play their own character.
Sounds like the sort of thing you would do when starting a new game - hand out pre-generated PCs to learn the ropes.
I have always found that a large part of the fun is creating the rest of the character, after the stats and abilities have been sorted out. Background, history, likes, dislikes, ties, antipathies, why he/she does what he/she does - these are all things I want to decide for myself.
My advice, for what its worth, is learn from this and don't do it again.
In the meantime, ask the player if there is a character he'd rather be playing?
BTW, I have killed another character but had good role-play reasons for doing it.
It meant that the rest of the party didn't try too hard to stop me being mauled and eaten by a Dire Ape, so I guess I got my comeuppance.