Does he have authority to do that? I understand the politics, but again, I thought the internals of the grand jury proceeding were secret.
Apparently, it was *unusual* for the Prosecuting Attorney to release the evidence; that too is usually kept private.
Here is a link to a pretty good article that addresses several of the questions raised on this thread.
http://blogs.wsj.com/briefly/2014/11/24/5-things-about-the-ferguson-decision/
If I recall correctly, I think the prosecutor petitioned the court to allow him to release the records.