Someone who Aids and Abets Criminal Conduct before the crime can be charged, as if he committed the crime. There is a large gray area there. From what I have seen, it appears that Tuscaloosa Police have a habit of overcharging.
In answer to your question, if two people are walking down the street and they get shot at and one pulls a gun and starts shooting back, the second that did not shoot back can probably not be charged with the crime. Now if two people are driving in a car and the passenger starts shooting out of the car and the driver speeds away, after the shooting, then there is a lot of explaining to the matter.