Hundreds of protesters poured into St Louis streets on Saturday, after a Missouri judge acquitted a former police officer who was charged with murder in the 2011 fatal shooting of a black man.
With the National Guard on standby in case of violence, authorities appealed to demonstrators to remain peaceful as they protested the outcome of the case - reminiscent of circumstances that spawned racially charged unrest in the nearby suburb of Ferguson, and gave rise to the Black Lives Matter movement in 2014.
Police said several protesters threw rocks and water bottles, while officers were seen in video footage and by eyewitnesses dousing at least five people with pepper spray, about a block from the courthouse.
As night fell, police reported making 13 arrests and said officers had been assaulted. A group of demonstrators tried to enter Interstate 40, but were blocked by police officers in riot gear.
Former city policeman Jason Stockley, aged 36, was found not guilty of first-degree murder in the shooting of 24-year-old Anthony Lamar Smith, in a verdict rendered by a judge five weeks after the end of a non-jury trial.
Mr Stockley and his partner chased Mr Smith, who was shot five times in his car. Defence attorneys said the former policeman believed Mr Smith was armed.
A gun was found in the car, but prosecutors argued Mr Stockley planted the weapon, as the gun only had Mr Stockley's DNA on it.
Following the verdict, some 600 protestors marched through downtown St Louis chanting, "No justice, no peace" and "Hey! Ho! These killer cops have got to go!"
Reuters / Newshub.