Just like CTH, you are making that statement in the absence of any facts and in direct contradiction of the statement of bikers at the scene.
Ironically enough the same contributor to CTH posted another piece blasting the Washington Post for using one source for a description of the shooting. This as opposed to his CTH articles which use one second hand account to come up with completely unfounded conclusions.
I personally would doubt any statement taken from a Cossack, with the exception of one very important issue. If the police were doing all of the killing, why do two different Cossacks give the same account of the first three Cossacks getting shot by Bandidos? Why wouldn't they they tell the truth?