Ok I orginally thought this was drug related. Now, with all of this new info, I have a new theory.
My current working theory is: (and all MOO)
Brittany heard that Uncle DH was soon to be questioned about sex crimes. By all accounts she liked this uncle. She then decided she wanted to go talk to him, to see for herself, so to speak, what he had to say concerning this. Uncles DK and SW, hear that BW is going to talk to Uncle DH and they in no way want him talking to BW, much less the police. So Uncles DK and SW offer BW a "ride" in Uncle DK's white truck. They proceed to kill BW and dump her body near Uncle DH. They call DH and tell him what they have done. They also tell him that if he implicates them when talking to the cops, that they will implicate him in the death of BW, because the body is located near his location. The next morning either one of two things occur- A. Uncle DH feeling that the net has tightened and he has no other way out, commits suicide or B. SW and DK not trusting that he will keep his mouth shut, go ahead and eliminate him theirself.
THIS IS ALL COMPLETE SPECULATION BASED ON RUMORS.
Now go ahead and pick my theory apart, maybe we will come up with something useful...