This could possibly be Wilson's version. Someone claiming to be a friend of his reported this version to the media, and a source close to the investigation told CNN that this matched what Wilson has told investigators.
Michael Brown rushed officer, radio caller says - CNN.com
The St. Louis prosecutor says that witnesses will start to testify before the grand jury as soon as Wednesday.
Edit: In Missouri, the prosecutor's office can either go through a grand jury, or bring a charge themselves and try to show probable cause in a preliminary hearing. In a case like this, I think the grand jury is the best route. Not just because of the politics involved, but in any case where "reasonableness" could be the determining factor. Where the line of criminality might be grey, and where actions are judged against societal opinions of reasonableness.