We essentially already knew this because Darren Wilson has testified to the Grand Jury already.  Wilson would traditionally be nearly the last to be questioned.  The prosecutor is now confirming the investigation is over.   Now they need to time the release of the Grand Jury decision in an attempt to minimize the looting and violence.

(CNN) — The investigation into the controversial shooting death of unarmed teenager Michael Brown by a police officer in a St. Louis suburb has been completed, the St. Louis County prosecutor’s office said Wednesday.
Ferguson police Officer Darren Wilson shot and killed the 18-year-old in the middle of the day on August 9 after allegedly telling Brown and a friend to get out of the street.
Authorities could have charged Wilson themselves by filing a criminal complaint, but St. Louis County Prosecuting Attorney Robert McCulloch instead opted to present the case to a grand jury to decide whether to indict the officer.
“The investigation has been basically completed that is being conducted by both the FBI and St. Louis County PD,” Ed Magee, the spokesman for the prosecutor’s office, told CNN.
A grand jury is expected to decide by the middle of next month if Wilson will be charged criminally for the shooting, which sparked weeks of unrest on the streets of Ferguson and calls for a federal civil rights investigation. (read more)