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ST. LOUIS, MO (KTVI) - What started out as a peaceful protest became aggressive Thursday in south St. Louis.

St. Louis Police Chief Sam Dotson says police moved into a crowd of protestors Thursday night because some of them became violent.

Dotson said at one point, a knife was thrown at an officer as well as rocks and bricks.

There was some property damage during the protests including a pharmacy and a police car.

Dotson says several flags were torn down and burned by unruly protestors.

Two people were arrested.