Who brought down MH17?

The answers start with the control tower information! That information was seized by " unknown military dressed in uniforms " who also seized some of the controllers " then a secret agreement was signed allowing any of the signers to veto release of any information or the whole report on the downing strangely the Ukraine was a suspect and one of the secret partners?
NATO was conducting military exercises in that area, with well over 4,000 radars recording air events the allies could only release you tube videos as proof of the rebels guilt?