The facts could lead to a felony. Yes, he can fight the charges. Yes, he should contact a public defender immediately, and he should not talk to anybody else about the incident (including you).
The public defender will probably not talk to him or be assigned until the day he shows up in court. Then look carefully at the police report and really question your son, if there was a parafin test and it shows residue from gunpowder on his hand or clothes he may be quilty, then he might want to join the military to avoid a conviction if the judge allows it.
My name is Stephen R. Cohen and I have practiced over 38 years and can be reached at 213-819-1171. I practiced mainly in Los Angeles and Orange County, California. I am not seeking clients from existing relationships with other attorneys, and give only limited advise over the phone (the phone is primarily used to set appointments), these services do not create an attorney client relationship. I apologize for mispelling< as I am a lousy typist, My answers may offend as I do not believe in pulling punches or sugar coating the truth. Further regarding courts in other states my opinions are largely based on logic and what I think is the modern trend which is to consider the needs of the child.