Why did the police hide evidence?

Last night, Newshub released explosive footage showing people working in the Pike River Mine with breathing masks after the explosion. The video was apparently taken by police, who controlled the mine at the time, but has been kept secret, even from the post-explosion inquiry. Obviously, it raises questions about whether the mine is safe to enter for a retrieval mission, and the government will have to answer those questions to the families of the victims. But it also raises real questions about the actions of the police - and specifically where they get off thinking they get to decide what a commission of inquiry gets to see and not see. The police appear to have deliberately withheld evidence and willfully obstructed the commission of inquiry in its investigation. And that's a crime. Those responsible need to be held accountable for it.