IMO Billy was inside. He asked Chris to call his phone , Chris was by the door or walked towards the door to listen for the phone ring. Then Jake or George shot Chris at the door. Chris stumbled or fell from the force of the shot in his arm. At that point Gary sees Chris gets shot, he turns to Billy a short scuffle happens. In which Gary hits Billy (causing the mark to his hand that the ME mentioned) in the eye causing the black eye Billy had at the funerals. Billy shoots Gary in the back of the head he goes down lands on his stomach. Jake and George enters after hearing the first shot. And then Chris is killed and more shots fired into Gary . Or Gary could have been shot the next 2 times and the Chris was shot. MOO