Two men, this is really kind of strange. I wouldn't think drug related, in the "normal" sense, though the killers and victims could have used drugs. No one was operating at that kind of scale, but personal revenge killings aren't often carried out with another, except in certain cases. Maybe a guy tells his friend I am going to scare my baby Mom, she's on some bullshyt, and things spiral out of control, and you end up killing everyone who witnessed it. Need more details about the crime scene to really get an idea.