So he's completely sane and he's in his early twenties he falls in love with this girl and they get married and have a baby. Due to something he had done illegal of course in his past (I guess it's Carl Powers and one of his brothers blamed him or something. You figure it out.) this group of big men storm their house and threaten to kill his wife and baby in front of him. He begs them not to, anything but them. They shoot her straight in the forehead while she still holds their child, they let him take his crying child. While he tried to calm the child, rocking s/he in his arms on of them shoots the baby and that's when he goes insane, he continues to say the soothing things he was saying before the child died, as if the child is still alive. A neighbour had heard the first gun shot the one that killed his wife and had called the police so they got there just before the shooters left and they went to jail (you can change the punishment to death sentence if you want. It'd make sense as they killed a child.) the whole time Jim is there with his dead baby in his arms. They take him to the place where insane people go. He gets out in under a year because he learnt how to act sane you know because he is a genius and he wiped all evidence of him ever being there and started his web of crimes.
As I was writing this I kept on expanding my ideas. It started as he got married and how his wife and baby died. I guess it's a prequel to Sherlock.