What happened in Waco? Several biker gangs met at a large bar. A fight started in the bathroom, and despite the presence of 12 policeman, it became general and 9 people ended up killed.
My question: Why were so many members of so many gangs there in the first place, and fully armed?
Conjecture: Merger talks. Leaders wished to talk about consolidating their drug businesses. They did not wish to meet as a small group because they feared murder. Or, perhaps, they wanted a chance for their guys to rub shoulders in a friendly environment— but in that case, they would have banned guns. They knew the danger of their guys rubbing shoulders together, especially if the leaders were occupied and couldn't supervise them. But they needed Mutually Assured Destruction. No leader would kill a rival leader (and, say, his 3 bodyguards, which could be done simultaneously) without igniting a bloodbath of revenge. To be sure, there was some possibility of a bloodbath by accident–a "finite tremble"— but that was worth the risk, ex ante. Ex post, of course, the merger talks have failed and police scrutiny will be intense. But that's just a risk of the MAD strategy.