An off-duty police officer shot and killed a black teenager in St. Louis on Wednesday night, setting off a demonstration just days ahead of long-scheduled protests in Missouri about the use of lethal force by the authorities.
The St. Louis police chief, D. Samuel Dotson III, said at a news conference that the teenager had fired at least three shots toward the officer, a six-year veteran who was working in the city’s Shaw neighborhood for a private security firm. Chief Dotson said that the officer had fired 17 rounds, but that he did not know how many times the teenager had been hit.
The teenager’s family disputed the police account, and a woman who said she was his cousin told The St. Louis Post-Dispatch that he had been unarmed.
“He had a sandwich in his hand, and they thought it was a gun,” the cousin, Teyonna Myers, told the newspaper. “It’s like Michael Brown all over again.”
Mr. Brown was unarmed when he was fatally wounded by a police officer in the St. Louis suburb of Ferguson on Aug. 9, and his death set off demonstrations that included bouts of violence and unrest. A grand jury in St. Louis County is considering whether to indict the officer who shot Mr. Brown, Darren Wilson.
Chief Dotson did not name the teenager or the officer involved in Wednesday’s shooting, but said the officer’s actions were under review by police officials who are members of a newly formed unit that investigates lethal force episodes.
At a news conference early Thursday, Chief Dotson said that the gunfire began after the teenager and others with him fled from the officer. The officer and the teenager who was killed, Chief Dotson said, eventually became involved in “a physical altercation.”
Soon after, the chief said, the teenager fired a handgun toward the officer, prompting the officer to open fire.
Word of the shooting quickly spread, and Chief Dotson said that several police cars were damaged during ensuing demonstrations. No arrests were made.
“No businesses were looted,” Chief Dotson said. “No windows were smashed, and I hope that continues to be.”
The Associated Press reported that much of the crowd had dissipated by about 1 a.m.
Chief Dotson said the teenager who had been killed was “no stranger to law enforcement,” but he declined to elaborate.
The shooting took place as the St. Louis area prepared for a planned “Weekend of Resistance.” Organizers have scheduled protest marches, acts of civil disobedience and, on Sunday night, a mass meeting at Chaifetz Arena, which is on the campus of Saint Louis University.
It is unclear how many people will participate, but organizers have said they expect thousands. Major labor organizations, including the A.F.L.-C.I.O., are supporting the weekend’s activities.