He’s an adult - first, for engaging in an adult behavior 8 months before, second because he absolutely did appreciate the gravity of what he was doing. It was his stated intention to assault her and kill her baby - this is an open and shut question IMHO.
Try him, convict him, execute him. Maybe it’ll save some other poor baby. It’ll certainly save the world from having this sick SOB reproduce any more.
Even though he can be tried as an adult, he can't get the death penalty because he isn't 18. Max is life in prison. Don't know if he can even get life in prison without parol (but don't think so).