If a time lord gives you a chance to go back in time but only to stop one serial killer, would you do it and who would you choose?

And if you so choose to do the mission, how far would you go in stopping this serial killer? Serial killer list

Would you wait till he kills his first victim to make certain he is guilty? Would you simply warn his victims and be satisfied with that? Would you be willing to kill him or would you just call the police? How would you make it all work?

Would you even try altering this killer’s past life gambling that that might prevent him from turning out to be a killer?