User blog comment:Peter Griffen Boy/Three questions./@comment-1647479-20100708150812

Three major members of Dutch's old gang were Bill, Javier, and John, being led by Dutch. Ross simply used John to kill all the others, and then finished the job himself. It can be assumed that Ross did it for prestige after you've seen the cutscene from "And the Truth Will Set You Free." And on a side note, Sheperd's ghost, you made my day.