Protests in St. Louis turned violent Friday night after remaining largely peaceful throughout the day.

Thirteen people were arrested and four officers were assaulted during protests in downtown St. Louis Friday afternoon. Interim Chief Lawrence O’Toole says the officers suffered minor injuries: one sustained a hand injury and was treated at the scene and release. The other three refused medical attention. One of those officers was struck in the head with a water bottle, one was knocked off their patrol bike, and another was pinned on the patrol bike.

O’Toole says the first person was arrested at 14th Street and Washington Avenue around 11 a.m. for damaging a police car. That person was charged with destruction of property and failure to obey.

Twelve more people were arrested at 315 S. Tucker Blvd. for offenses ranging from second-degree assault on a law enforcement officer to failure to disburse. O'Toole says officers deployed mace after an officer was hit with a water bottle, and they're wearing protective gear because they've been hit with objects.

After dark, protesters headed to St. Louis Mayor Lyda Krewson's home and threw rocks at her windows.

Meanwhile, agitators in the Central West End threw a brick at a police line, seriously injuring an officer. That's when officers began to spray tear gas in attempts to break up the crowds.

PHOTOS | Protests in downtown St. Louis after Stockley decision

Earlier in the evening, around 6:30 p.m. protesters gathered in the Central West End. They marched through the neighborhood, chanting and holding a sit-in. It wasn't until after dark that the protests turned violent.

Judge Timothy Wilson's decision to find former police officer Jason Stockley not guilty of first-degree murder and armed criminal action for the 2011 shooting death of Anthony Lamar Smith was announced shortly before 9 a.m., and protesters started gathering near the Civil Courts building at Market Street and Tucker Boulevard, peacefully demonstrating their opposition to the decision.

They marched to the on-ramp of I-64 at Clark Street, but officers on bicycles formed a human chain to prevent them from shutting down highway traffic. The protesters left that area without any physical confrontations.

Police use cars and bike teams to block the entrance to Highway 64 as protesters walk through the streets of St. Louis following the announcement of a non-guilty verdict of a former white St. Louis policeman in the 2011 shooting of a black man, in St. Louis on September 15, 2017. Jason Stockley was acquitted of first degree murder charges in the fatal shooting of Anthony Lamar Smith on Dec. 11, 2011 following a high-speed chase. Protesters have vowed civil disobedence. Photo by Bill Greenblatt/UPI

Demonstrators then walked north on 14th Street and then east on Washington Avenue. Around 1 p.m. demonstrators gathered along Tucker between Spruce and Clark streets. Police say officers were on buses to leave the area, but they were blocked in by protesters who threw rocks at the buses.

SEPTEMBER 15: Protestors march through St. Louis streets following a not guilty verdict of former police officer Jason Stockley, who was charged with first-degree murder in the shooting death of Anthony Lamar Smith. 

5 On Your Side reporter Jacob Long saw police use pepper spray on a protester who appeared to be blocking a Metro bus.

Later in the afternoon the protesters continued to walk around downtown St. Louis, heading back to Washington Avenue and then toward the Riverfront.

Some schools have closed and some events have been postponed through the weekend.