Eight police officers were injured in clashes with demonstrators in St Louis when a largely peaceful protest turned violent in the early hours of Saturday after a Missouri judge acquitted a former white police officer of murder in the 2011 fatal shooting of a black man suspected of dealing drugs.
The clashes erupted when police confronted a small group of demonstrators as the protest moved, over the course of the evening, from the courthouse where the verdict was read to a busy nightlife neighborhood.
After most protesters drifted away, a smaller group of individuals police described as "agitators" lingered on the streets in an upscale neighborhood near the mayor's home, taunting officers who arrived in riot gear by the busload.
Police used tear gas and rubber bullets to control the crowd as vandals broke windows at a library, a restaurant and a home and threw bricks and water bottles at officers.
Police reported making at least 13 arrests. Three officers were taken to hospital.
"Reports of bricks thrown at police. That's not protest. That's a crime. We stand behind our officers. This violence won't be tolerated," Missouri Governor Eric Greitens said on Twitter.
With National Guard troops placed on standby, authorities urged calm in the aftermath of a case reminiscent of the circumstances that spawned racially charged unrest in the nearby suburb of Ferguson, giving rise to the Black Lives Matter movement in 2014.
One group of demonstrators tried to climb onto Interstate 40 but were blocked by police. Another group blocked an intersection by sitting down in the street for six minutes of silence.
The outcry was prompted by Friday's verdict, rendered five weeks after the conclusion of a non-jury trial, finding former city policeman Jason Stockley, 36, not guilty of first-degree murder in the shooting death of Anthony Lamar Smith, 24.
Smith was shot five times in his car after trying to flee Stockley and his partner on Dec. 20, 2011, following an alleged drug deal, authorities said.
During the pursuit, Stockley could be heard saying on an internal police car video he was going to kill Smith, prosecutors said.
At Stockley's direction, his partner, who was driving, slammed the police cruiser into Smith's vehicle and they came to a stop, court documents said. Stockley then approached Smith's car and opened fire with his service weapon.
The former policeman believed Smith was armed, defense attorneys said, and a gun was found in the car. But prosecutors argued Stockley planted the weapon and that the gun had only Stockley's DNA on it.