CLAYTON, Mo. -- A grand jury has decided not to indict Ferguson Police Officer Darren Wilson for killing 18-year-old Michael Brown , St. Louis County Prosecuting Attorney Robert McCulloch announced Monday.

McCulloch said members of the jury met for 25 days and heard over 70 hours of testimony from over 60 witnesses before reaching their decision. He confirmed Wilson had fired 12 shots at Brown, who was unarmed.

Brown's Aug. 9 death sparked massive demonstrations in the St. Louis suburb of Ferguson and a national conversation on race and law enforcement. Activists had predicted a new wave of demonstrations if Wilson was not indicted -- not only in Ferguson, but in the greater St. Louis region and in other cities across the country.

"We are profoundly disappointed that the killer of our child will not face the consequence of his actions," Brown's family said in a statement. "While we understand that many others share our pain, we ask that you channel your frustration in ways that will make a positive change. We need to work together to fix the system that allowed this to happen."

McCulloch said he would release full transcripts of the grand jury proceedings Monday night. His office took an unusual approach to the grand jury process by simply presenting the panel with all the evidence but not recommending any specific charges against Wilson.

"From the onset, we have maintained and the grand jury agreed that Officer Wilson's actions on August 9 were in accordance with the laws and regulations that govern the procedures of an officer," Wilson's lawyers said in a statement. "Law enforcement personnel must frequently make split-second and difficult decisions. Officer Wilson followed his training and followed the law."

Witnesses to Brown's shooting who have publicly spoken about their recollections largely told the same story about the events that led to his death.

It is well established that Brown and his friend Dorian Johnson were walking in the middle of a quiet residential street near the home of Brown's grandmother when Wilson confronted them shortly after noon on Saturday, Aug. 9. The witnesses who spoke publicly said there was an initial confrontation between Brown and Wilson through the window of his police SUV -- some said they thought Wilson was trying to pull Brown in, while Wilson has reportedly said that Brown reached for his weapon.

Wilson reportedly fired one shot out the window, and witnesses claim that Brown took off running. Wilson emerged from the vehicle, and Brown at some point turned around. Many witnesses who have spoken publicly said that Brown looked like he was trying to surrender and put his hands in the air as Wilson shot the final fatal rounds. Wilson reportedly contends that Brown was headed back toward him.

The Washington Post, meanwhile, reported that seven or eight witnesses largely backed up Wilson's account of the shooting in testimony before the grand jury. Those witnesses, like most of the people in Ferguson, are African-American.

When Ferguson Police Chief Tom Jackson released Wilson's name on Aug. 15, the police department simultaneously released a video that appeared to show Brown stealing cigarillos from a convenience store not long before the shooting and shoving a clerk when he was confronted. Jackson has since said that Wilson was not aware that Brown had been involved in any alleged robbery when the officer spotted him on the street.