An 18-year-old man has died after an off-duty police officer shot at him 17 times - just miles from where unarmed teen Michael Brown was gunned down by a cop in August.

Police said that Vonderrit Myers Jr. first opened fire on the unidentified 32-year-old officer in Shaw, Missouri, which is less than 10 miles from Ferguson, where Brown was shot dead on August 9.

The officer, who is a six-year veteran of the force, was in a car working a secondary job for a private security company and paroling the area when he saw three males in the street and thought they were acting suspiciously, St Louis Police Chief Sam Dotson said in a press conference.

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Killed: Vonderrit Myers Jr., pictured left with his mother and right, was shot dead by an off-duty police officer on Wednesday night. Police said he fled when approached by the officer and a fight ensued

Crime scene: A crowd gathers near the scene at Shaw Boulevard where the teen was fatally shot on Wednesday - just miles from where unarmed teenager Michael Brown was shot by a cop in August

Anger: Crowds confront police near the scene in south St. Louis after the 32-year-old officer killed the teen

As he approached them, one of them started to run away, so the officer did a U-turn and then all three ran, Dotson said, the St Louis Post-Dispatch reported.

'One of them ran in a way that the officer believed that he was armed with a gun – holding his waist band, not running at full stride,' Dotson said, referring to Myers.

The officer, who was wearing a Metropolitan Police Department uniform, jumped out of his car and chased them on foot before getting into a scuffle with Myers, who reached for his gun, Dotson said.

Myers shot at least three times at the officer, who then returned fire - and when the teenager tried to fire again, his gun jammed, Dotson said.

Dispute: Myers, pictured, was just buying a sandwich before he was chased and shot dead, his family said

Authorities said Myers, in white, was known to them and was wearing a monitoring device on his ankle as part of the bail conditions for a previous arrest for gun charges. He was due to go on trial in November

Street fight: Cops say that the teen shot at the off-duty office first and then he shot back, killing him

The officer, a white male, then fired 17 times at the teenager - but it is not yet known how many times he was struck and Dotson said he doesn't know why he fired so many times. He died from his injuries.

Police recovered a 9mm Ruger at the scene, he said.

The officer was working for Hi-Tech Security, which employs several St. Louis police officers in secondary jobs. He was patrolling the neighborhood on behalf of the company rather than the Metropolitan Police Department but was wearing his police officer's uniform.

He has been placed on administrative leave and an investigation is underway. He was not hurt.

Dotson said that the 18-year-old was 'no stranger to law enforcement', the St Louis Post-Dispatch reported.

He was wearing an ankle bracelet at the time as a condition of bail in a gun case, according to his lawyer and police, the Post-Dispatch reported.

The newspaper reported that Myers was due in court in November for unlawful use of a weapon and resisting arrest after he allegedly ditched a gun after jumping from a car that had been involved in a high-speed chase.

Backup: The 32-year-old officer, who has not been identified, was not on duty when he shot the boy

Protest: People at the scene put up their hands, like the protesters who showed they were not armed in the aftermath of the killing of Michael Brown. Protests still continue in the area following that death in August

Police caught him nearby and recovered the loaded .380-caliber pistol he had allegedly dropped.

He was jailed for a few days before being released on $1,000 cash bond and fitted with an electronic monitoring device.

He was allowed to leave his home for work, school, court appearances, meetings with attorneys and meetings with the private monitoring firm, the Post-Dispatch reported.

His family said he was still in high school and disputed police claims that he was armed.

'He was unarmed,' said his cousin, Teyonna Myers, to the Post-Dispatch. 'He had a sandwich in his hand, and they thought it was a gun. It’s like Michael Brown all over again.'

The boy's uncle, Jackie Williams, also says he is not buying the story being told by police.

'My nephew was coming out of a store from purchasing a sandwich. Security was supposedly searching for someone else. They Tased him,' Williams said.

'I don’t know how this happened, but they went off and shot him 16 times. That’s outright murder.'

Nearby: The incident unfolded less than 10 miles from where Michael brown (above) was killed in Ferguson

Officers are claiming they recovered a gun at the scene and that the officer did not have a Taser.

Another man, Lavell Boyd, who lives in the neighborhood, claimed to hear as many as 15 shots fired.

'When I pulled up I saw the cop standing over him [Myers] then he pointed the gun at everyone else telling everyone to get back while he was searching for another clip,' Boyd said.

News of the death quickly spread across social media and sparked more protests in the street - just the latest outcry after the death of Michael Brown.

David Carson, a photographer for the Post-Dispatch, reports that protesters filled the streets near where the shooting happened and have been chanting 'Black lives matter.'

Some also vandalized a police SUV as they chanted 'F*** the police.'