The prosecutor must prove beyond a reasonable doubt all elements of the crime. The mere fact that you were there does not shift the burden to you. As I do not know the statute under which you were charged, I can only speculate that the act of shooting itself in the locale you were shooting from was reckless. If the crime in MI requires that you hit something off target then the prosecutor would have to prove all the elements you mention. You need a lawyer badly; get one.
The prosecutor must prove your guilt beyond a reasonable doubt. Crimes have what lawyers call "elements". Each of these "elements" must be proven at trial "beyond a reasonable doubt" before you can be convicted of a crime. Mere presence where a crime is committed is not sufficient. Your best bet is to contact an experienced Michigan Firearms Attorney. Visit www.self-defense-law.com.