While it is doubtful that all the gangsters in Waco were shooting, it is not uncommon to arrest and charge all the physically present members of say the Crips, Bloods or Cossacks.
Liuke I say, the news sources that are telling you that all the groups where were akin to Crips and Bloods, are LYING TO YOU. You would know this if you did your due diligence, where you will eventually come upon the actual invite and announcement of the meeting and the various groups invited.