The crime will have to be severe (it is) and there will have to be clear evidence of malice. In the case of poor judgment I suspect they will probably not try him as an adult.
Just my thoughts.
As for what I think should happen to him, no comment. I have no idea what should be done because I can not think of any scenario where sanity will prevail. The girl will stay dead, no matter what consequence Bell has to face. Destroying Bell's life by sending him to prison won't bring back the girl, and yet the girl's family deserves justice.
There are zero winners here, I'm just glad I'm not the one who has to make this decision.
"Pain or damage don't end the world. Or despair and beatings. The world ends when you're dead. Until then, you got more punishment in store. Stand it like a man... and give some back."