What Should Johnny's Sentence Be?

Please answer the following question with a 300-word response.

In August of 2014, a 12-year-old boy stabbed and killed a 9-year-old boy on a Michigan playground.  Prosecutors have decided to charge the 12-year-old as an adult.  If found guilty, what do you believe is the appropriate punishment for the 12-year-old?  Explain your position on what you think the sentence should be?  What factors have you considered to come to this conclusion?  Explain using case law.