A woman is sent to hospital during a protest in St. Louis, Missouri, the United States, Sept. 16, 2017. Police on Saturday put up barricades around the courthouse and police headquarters in St. Louis, Missouri, bracing for more protests that are expected to come in days. (Xinhua/Dane Iwata)

ST. LOUIS, the United States, Sept. 17 (Xinhua) -- Protesters smashed windows and other property in downtown St. Louis, U.S. state of Missouri, using baseball bats, concrete chunks, and even a makeshift metal spear Sunday night.

Riots in the city bordering Missouri and Illinois have entered a third night over the acquittal of St. Louis police officer Jason Stockley, who is accused of killing Anthony Lamar Smith, a 24-year-old black man, in 2011.

In this third night of riots, police confiscated guns, knives, a sword, pepper spray, and a shield from protesters. Police report that unknown chemicals were sprayed by protesters at police officers.

Protesters had spent much of the day disrupting city streets, marching from police headquarters to a local university. But by nightfall, much of the law-abiding crowd had dissipated.

More protests are scheduled for Monday and Tuesday.

Former police officer Stockley was found not guilty of first-degree murder and armed critical action on Friday, almost six years after the incident happened when he shot Smith five times after a high-speed car chase that ended with a collision.

Prosecutors said Stockley planted a gun on Smith, as Stockley's DNA was found on the gun but Smith's was not. Stockley maintains his statement that he was acting in self-defense.

Prior to the not-guilty verdict, Republican Missouri Governor Eric Greitens put the U.S. National Guard on standby in expectation of demonstrations, deploying some troops at points of critical infrastructure.