Earlier quoted context omitted.
Police acting as agent provocateurs is not new: http://www.cbc.ca/news/canada/quebec-police-admit-they-went-...
I get that. Is there evidence that the police were doing so in this case?
What we do have is narratives from bikers present, and some photographic evidence that raises doubts about who started it. There's a lot to discuss/research, so I'll just give you a couple links as major starting points. I'm not saying whether I agree/accept the theories or not, just that we don't have enough definitive evidence to support or deny the conspiracy theory.
Short version: police snipers were already positioned, an undercover agent either started something or was "made", a fight was provoked and police were strangely quick to start firing.
http://www.breitbart.com/texas/2015/05/19/biker-truthers-eme... http://theconservativetreehouse.com/2015/05/27/waco-twin-pea...
(Please don't launch into criticizing the messengers; this is about the message.)