User blog comment:JediSpectre117/Citadel Trailer is out REPEAT OUT !!!!!/@comment-5362182-20130304192834/@comment-2250460-20130304212546

At the end of Privateers, Garoth blames Shepard for his brother's death. Then in his second mission he joins with Cerberus and tries to kill Shepard.

That or this is all made up in my head, probably purposely so.