Jason Stockley, 36, was acquitted of first-degree murder for killing Anthony Lamar Smith, 24.
Butler said. "We will be non-violent but we will not settle on peace".
The case is notable because few police officers ever face trial in shooting deaths, and even fewer are convicted. They tweet, "Rocks & water bottles have been thrown at our officers throughout the day".
A video posted by Christian P. Bryant showed police in riot gear facing off with protesters.
Stockley, as to be expected, claimed that he had acted in self-defense, saying he believed that Smith was reaching for a weapon in the vehicle.
With the National Guard on standby in case of violence, authorities are allowing protesters to march peacefully despite the history of racial divides since the death of Michael Brown in Ferguson, Missouri, in August 2014. Anthony Lamar Smith was killed in 2011 during a confrontation with police. Maleeha Ahmad, 28, of St. Louis was maced along with several other protesters. Some tried to make their way onto Interstates 64 and 44 to block traffic, but police kept them away.
The verdict in the case against the former St. Louis officer, Jason Stockley, in the fatal shooting of Anthony Lamar Smith had been tensely awaited here.
And an Alzheimer's Walk scheduled for Saturday in downtown St. Louis was postponed.
Stockley opted for a bench trial rather than take his chances with a jury. "Agonizingly, this Court has poured over the evidence again and again", Wilson wrote in the order.
Al Watkins, an attorney for Smith's fiancee, said that people had a right to be angry about the verdict.
Clay is a Democrat who represents the St. Louis area. The defense said he went to get a "quick clot" pack to help slow Smith's bleeding from gunshot wounds.
Democratic Sen. Claire McCaskill and Republican Sen.
In recent years grand juries have declined to charge officers involved in the 2014 fatal shooting of Michael Brown, 18, which set of nights of violent protest in Ferguson, and the choking death of Eric Garner, 43, in NY.
Missouri Gov. Eric Greitens, anticipating protests in response to the controversial ruling, released a statement saying he understood the verdict is painful for many St. Louisans.
St. Louis Circuit Attorney Kim Gardner said to the Chicago Tribune that she was disappointed.
UNIDENTIFIED PROTESTERS: (Chanting) Our streets.
"I'm proud of these people protesting", Smith, who is black, told the Post-Dispatch. "Cops can still kill us with impunity". I'm very proud of my team's effort and commitment to the pursuit of justice on behalf of Mr. Smith's family and the people of St. Louis. Another group blocked an intersection by sitting down in the street for six minutes of silence. He is then seen going back to Smith's auto and entering the vehicle twice for several moments.
"The injustice of this verdict is heartbreaking to the community", she said.
Baruti said there will be more civil unrest. Who was also found not guilty of murder and the shooting was deemed self defense.
The mayor encouraged St. Louis residents to show each other compassion and recognize that they all "rise and fall together".
"For the most part, the demonstrations have been peaceful", the department tweeted.
"I pray for my city, man, 'cause my people exhausted of this", said Mike Brown Sr.
"While we know emotions are running high, our number one priority is protecting and serving our citizens".
The outraged protestors say, "The whole damn system is guilty as hell". Stockley was knocked "sideways" by the Buick and opened fire as Smith pulled out of the parking lot, shattering the car's back window.
Nationally, Stockley's acquittal is the fourth since May of law enforcers charged in questionable shootings of black men. The judge wrote that the statement "can be ambiguous depending on the context".
Johnson, who said Stockley imprisoned him only eight days before the lethal fight with his sibling in December 2011, joined demonstrators Friday evening to dissent the decision.
Wilson had been adjudging DNA evidence and deciding it was inconclusive, according to the state's own expert witnesses (which is true, another hole in the state's evidence - the absence of Smith's DNA on the gun allegedly found in his vehicle does not prove that he never handled the gun).
With Bianchi at the wheel, the officers chased Smith at speeds of more than 80 miles per hour before the crash, according to the criminal complaint.
Stockley left the police force in 2013 and moved to Houston. But prosecutors said that's when Stockley retrieved the gun, according to KMOV. Not conclusive of prior intent, Wilson ruled.
The Republican said the step was "a necessary precaution".