A black teenager was shot in the St. Louis suburb of Berkeley Tuesday night, sparking unrest just a month after a grand jury decided not to indict a police officer involved in the shooting of Michael Brown in near by Ferguson. In this case, police say the teen was armed and threatened the officer, who shot in self-defense.

An officer of the Berkeley Police Department shot an armed black 18-year-old teenage identified as Antonio Martin, according to KSKD. The shooting took place at a Mobil gas station at around 11:15 p.m. The officer, who has yet to be identified but is said to be white, 36-years-old and 6-year veteran in the department, was responding to a 911 call that said a robbery had taken place at the location.

Speaking at a Wednesday morning news conference, the St. Louis County Police chief Jon Belmar explained what happened at the gas station, reports the St. Louis Post-Dispatch.

When he arrived at the scene, the officer spotted two men standing near by. He began talking with them and one of them approached the driver’s side of the cruiser, where the officer was. Brian Milliken, the officer’s attorney, said the other man, Martin, kept walking away and the officer kept asking him to stay near him.

Then, one of the men "produced a pistol with his arm straight out, pointing it straight at the officer kind of from across the hood," said Belmar. The officer stumbled to the ground and fired three shots: one struck Martin, the other one of the cruiser’s tires and the third has not been accounted for.

However, the officer had been given a body camera but he was not wearing it when he opened fire. The police did release a security footage that shows the moments leading up to the altercation but it ends before the shooting, according to CNN.

The Washington Post’s Wesley Lowery posted photos on Twitter of the gun that was on Martin’s hands allegedly.

Police say the 9 mm gun has its serial number filed off, reports the St. Louis Post-Dispatch, with five rounds in the magazine and one in the chamber.

In the press conference, both Belmar and Berkeley Mayor Theodore Hoskins both expressed their condolences for the family of the victim, according to the Washington Post. But, they emphasized this incident was very different from the shooting of Michael Brown.

“You couldn’t even compare this with Ferguson or the Garner case in New York,” Hoskins said. “The video shows the deceased pointed a gun that has been recovered.”

He added that the majority black town had also a majority black police force as well as black civic leaders, including Hoskins.