(CNN) An 8-year-old girl was killed and three other people were injured in a shooting near a preseason high school football event Friday night in St. Louis, police said.

Investigators are looking for whoever fired the shots. The girl is the 12th child or teenager killed by gunfire in the Missouri city since April, the St. Louis Post-Dispatch reported

The girl, two teenage boys and a woman were shot near Soldan High School, police said. The girl had just attended a football jamboree -- a series of preseason scrimmages -- at the school with the two teens, CNN affiliate KMOV reported

Police officers already were in the area when the shooting happened, having started to clear crowds from the school grounds after fights were reported there, St. Louis Police Chief John Hayden told reporters.

The girl was "with family" when she was shot, Hayden said. He didn't say who her relatives were, or whether they were among the injured. He also didn't say what led to the gunfire.

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