A St. Louis grand jury Monday found no probable cause to indict Ferguson police officer Darren Wilson in the shooting death of Michael Brown.

St. Louis County prosecutor Bob McCulloch told reporters, "No probable cause existed in each of the five indictments," to indict Ferguson police office Darren Wilson.

"We are profoundly disappointed that the killer of our child will not face the consequence of his actions," Brown's parents said. They urged others who share their pain to "channel your frustration in ways that will make a positive change," the family said in a statement.

Activists across the U.S. staged their own rallies at federal courthouses nationwide in solidarity in Chicago, New York, Philadelphia, Pittsburgh and Seattle.

The father of black teenager Michael Brown, Mike Brown, Sr., asked for four minutes of silence on Monday before any protests start when the St. Louis grand jury announces it decision about whether to indict Ferguson police officer Darren Wilson.

The grand jury convened in mid-August and heard testimony for months about whether to indict the police officer for the shooting death of 18-year-old Michael Brown on Aug. 9.

The grand jury was to consider whether to charge Wilson with charges ranging from manslaughter to first-degree murder. Nine of the 12 jurors needed to return an indictment in order for the police officer to be charged.

A parallel federal civil rights investigation of the shooting is continuing. Federal investigators are also conducting a broader probe of the Ferguson Police Department.

On Aug. 9, police officer Darren Wilson fired six shots at Brown in Ferguson, a town northwest of St. Louis. Mr. Wilson stopped Mr. Brown and another man for walking in the street. Brown family lawyers and police accounts say a struggle between the officer and Mr. Brown took place inside the officer's cruiser, resulting in the firing of Mr. Wilson's pistol.

The absence of charges filed in the initial aftermath and the handling of the situation by local police enforcement drew national attention, with protests in Ferguson and in towns and cities across the U.S.

A spokeswoman for Missouri Gov. Jay Nixon, who declared a state of emergency and called in the National Guard last week, said the governor would be in St. Louis on Monday, but declined to say any more about his plans for the day.

On Friday, the St. Louis County police put up metal barricades around their main building in downtown Clayton. On Saturday, police and workers arranged barricades in front of the justice center where the grand jury has been meeting.