There is a Wikipedia page that deals with this fairly well at (
http://en.wikipedia.org/wiki/Maryland_self-defense).
In short the student is screwed.
Maryland has a "duty-to-retreat" which for the case of property being stolen like that, he has to retreat, go back into the house and call the cops. The only reason he could use deadly force is if his life is being threatened and he has nowhere to go.
If the prosecutor chooses not to file charges, that is his/her decision, but I really think that with the information given that Manslaughter could reasonably be charged and convicted on.