The law of parties is about conspirators. If you conspired to commit a crime then you are guilty of that crime. It's the difference between knowing and not knowing. If you had prior knowledge that a crime was about to take place, and you proceed to encourage or aid in the commission of that crime, then you will receive the same charges as the perpetrator of that crime. Whether you were just standing guard or you were the get away driver.
So if KJ told someone in that vehicle... Shoot at those guys when we pass by. Then he'll be charged with murder. And the same goes for the driver. The other guys in that SUV will be allowed to walk, because they didn't take part in the crime. So the law of parties may not apply to everyone in that SUV.