I do not believe for a second that this had anything to do with drugs.
If this was a "big drug deal" it wouldn't have gone down on a public trail. These things go down in abandoned buildings, in someone's home, or even in an abandoned parking lot. Nobody goes through the trouble of hikinh through the woods to do a drug deal, only to have it go down on a public trail, where anybody can pop up at any time.
Furthermore, I don't understand why anybody who was spotted dealing drugs would go through the trouble of marching the girls through the woods, possibly across a creek, just to execute them. If the offender was so worried about being caught, why not execute them on the bridge, then get away as quickly as possible?
Contrary to popular belief, drug dealers don't want to kill people. They want to sell drugs and make money, and may kill in the event there's a debt owed, or someone may be going to court to testify against them. I honestly don't think it makes too much sense to kill two kids, on a whim, because they saw you selling drugs....you just leave. To go from drug dealing to double murder in this way, makes no sense to me.
As far as tips go, we absolutely have no idea who's called in what, about whom. So it's not fair to assume BG hasn't been ratted out yet. As far as COD, we don't know. LE has not released this information yet, so we have no idea whether there was or wasn't a sexual component to this case. Even if there was, DNA is something that may not be readily available. There are "non-secreters" that exist in the population, and although a minority, they are out there.
In cases like this, the most simple explanations are usually the best. Either BG knew the girls, in some way, or he didn't, and they ran into a dangerous pervert out there in the woods that day. He has a predilection for young girls, and saw an opportunity and decided to act. Whether or not he's done it before is debatable..but what's not is the distinct possibility that he'll do it again.
Sorry for rambling, but the drug thing makes no sense. Of course, there has been no evidence released to support my theory either, so I can be 100% off.
Everything above is MOO.