File Photo: Toni Martin, front center, cries out on as she talks to police at the scene where she says her son, Antonio, was fatally shot in Berkeley. (Associated Press)
A police investigation has confirmed that a black US teenager was brandishing a gun when he was fatally shot by a white officer in Missouri, officials said on Tuesday.
The December 23 death of 18-year-old Antonio Martin took place at a gas station in the St Louis suburb of Berkeley, near the town of Ferguson, where unarmed black teenager Michael Brown was shot dead by a white officer in August.
Brown's shooting sparked a nationwide wave of protests against police, and hundreds of demonstrators again took to the streets following the Martin's death.
However, unlike in the Brown case and other high-profile police killings this year, Martin was carrying a weapon and threatened to shoot at police, officials said.
A probe found that Martin pointed a handgun at a police officer who was responding to a shoplifting call at the service station.
"Basically, Mr Martin was armed, Mr Martin did... attempt to fire when he pulled a weapon on the officer," Berkeley Police Chief Frank McCall told reporters.
"The officer, in fear of his life, retreated and while doing so, fired approximately three rounds."
McCall said several witnesses had corroborated the police version of events. And a grainy video depicting part of the incident appears to show someone raising a weapon.
The officer has not been named.
According to the St Louis Post-Dispatch newspaper, McCall said a live cartridge was in the chamber of Martin's gun, with five more bullets in the clip.