St Louis police shooting: Off-duty officer kills black teenager Vonderrick Myers sparking new 'Hands Up Don't Shoot' protests

Those demonstrating say 18-year-old high school student Myers was shot 17 times - and holding a sandwich rather than a weapon

Crowds confront police near the scene in in south St. Louis where a man was fatally shot by an off-duty St. Louis police officer on Wednesday, Oct. 8, 2014 (AP)

An off-duty police officer in St Louis has shot and killed a black teenager, prompting a repeat of the Ferguson protests that followed the death of Michael Brown two months ago today.

Police in the already conflict-ridden county of Missouri said that the officer involved was wearing his uniform but working a second job as a security guard when the incident occurred late on Wednesday night.

The officer, who is 32 years old and white, was unharmed in the incident.

Pictures from the scene on Shaw Boulevard in south St Louis showed people gathering to protest the shooting. KTVI News reported that the crowd was preparing to march on the St Louis police station, with many chanting "hands up don't shoot", a slogan that was used across the US after Ferguson.

As with the death of Michael Brown, there were conflicting initial reports on whether or not the victim, who has been named locally as 18-year-old Vonderrick Myers, was armed.

Teyonna Myers, 23, told the St. Louis Post-Dispatch newspaper that she was the cousin of the man and that he was unarmed when he was killed.

"He had a sandwich in his hand, and they thought it was a gun. It's like Michael Brown all over again," she told the paper.

St Louis Public Radio quoted chief of police Sam Dotson as saying that the officer fired "17 times", while alderman Antonio French, on the scene with protesters, tweeted: "At the scene of yet another young man's death. This happens too often in our city. It's a crisis that we should all be concerned about."

He later wrote: "The victim's mother was here. She fainted. An ambulance came to attend to her. There is nothing like a mother's pain at the loss of a child."

But a spokesperson for St Louis Police, Colonel Alfred Adkins, said the officer - who has not been named - approached Myers and three other men in the street and only "returned fire" after he was shot at himself.

"As [the officer] exited the car, the gentlemen took off running. He was able to follow one of them before he lost him and then found him again as the guy jumped out of some bushes across the street," Adkins said.

"The officer approached, they got into a struggle, they ended up into a gangway, at which time the young man pulled a weapon and shots were fired. The officer returned fire and unfortunately the young man was killed."

Police said a gun was retrieved from the scene near Missouri Botanical Gardens.

Another spokesperson, for the St Louis city police division, said the officer was a six-year veteran of the department. He has now been placed on administrative leave, she said, and an investigation into the incident is ongoing.