ATLANTA (AP) — A protest has turned violent in downtown Atlanta in the wake of the killing of an environmental activist by authorities. Officials say the 26-year-old shot and wounded a state trooper. Masked activists dressed in all black threw rocks and lit fireworks in front of a skyscraper that houses the Atlanta Police Foundation on Saturday evening. They lit a police cruiser on fire and vandalized other buildings with anti-police graffiti. Authorities say they made six arrests and halted the violence. The activist, who went by Tortuguita, was killed Wednesday as authorities cleared protesters from the site of a planned public safety training center. Authorities say the trooper fired in self-defense, but activists question that account.